A structure-based analysis of morphosyntactic regularities in language-contact.

Eric Hoekstra, Frisian Academy, Ljouwert

In J.W. Zwart and W. Abraham (2002, eds) Studies in Comparative Germanic Syntax. John Benjamins, Amsterdam, 277 - 291.

1. Introduction [note 1]

Languages develop by language contact. There are always two or more competing language variants. A language changes by introducing new variants, and by ousting old variants. Sometimes a whole language gets replaced by another. We may then speak of an advancing language and a receding language.

A receding language and an advancing language may together give birth to language varieties which are in an intuitive sense "intermediary" between the receding language and the advancing language. A receding language is usually the mother tongue of speakers whereas an advancing language typically advances as a second language. (Here we are, talking English, while our mother tongues are Dutch, Frisian or German). Speakers switch from the mother tongue to the second language. Due to imperfect acquisition, however, they impose syntactic structure of their mother tongue onto the imperfectly acquired second language. [note 2] For their children, however, the imperfectly acquired second language will be the new mother tongue. The new mother tongue will be an intermediary between the advancing language and the receding language.

Frisian is such a receding language, and in the process of recession before Dutch it has given birth to such language varieties as Town Frisian, Bildts and West-Frisian. [note 3] Furthermore, in the process of recession before Saxon dialects Frisian has given birth to the Hogeland dialect (including Westerkwartier) of Groningen (see map 1). For ease of reference, I will refer to the Hogeland and Westerkwartier dialects as the Groningen dialect, though this is not, strictly speaking, correct.[note 4] Thus, we find contact-based dialects in the area where once Frisian was spoken.

If we consider the contact dialects, we note that certain properties of Frisian survived in the contact dialects, whereas other properties did not survive. Why should that be so? In order to answer that question, we turn to theories of language contact, such as Kaufman & Thomason (1988) and Van Coetsem (1988) and subsequent work. Kaufman & Thomason point to the relevance of social factors for the process of language contact. Van Coetsem analyses the relevance of linguistic factors. Thus these two works are complementary, in my view.

The purpose of this article is to be more specific about the mechanisms at work in dialect contact. To be able to do so, we will compare a number of dialects which are all to a greater or lesser extent based on language contact between Frisian and either Dutch or Saxon as a second language. This yield some interesting empirical results, which we will try to accommodate by a refinement of language contact theory.

Such a refinement is called for not only because of the empirical considerations to be presented below, but also because of theory-internal considerations. The theory as it stands claims that the syntax of the mother tongue tends to be projected into the new language and the phonology of the second language. This presupposes that syntax and phonology are separate from each other. Clearly, they are not: agreement, a syntactic notion, is expressed phonologically in the form of affixes consisting of specific phonemes.

2. The theory

According to the theory of Van Coetsem, syntactic structures are transferred from a mother tongue into a second language, in case a second language, usually a status language, is inadequately acquired. Hence the syntax of contact dialects often betrays what was the original mother language when the contact dialect came into existence. The theory is based on insight from second language acquisition. Following Van Coetsem (1988) and others we distinguish between two cases: linguistic aspects which are below the level of consciousness of the language user and those which are above it. Van Coetsem proposed that elements of the grammar which are below the level of consciousness are hard to learn and therefore easily projected from the mother language into the target language. Research by Van Coetsem (1988), Van Bree (1997) and others indicates that the following elements of grammar are largely below the level of consciousness: phonetics, morphology of unaccented syllables, syntax. On the other hand, elements which are above the level of consciousness are easily learned and taken from the target language. These include: content words, phonemic correspondences, morphology of accented syllables. In this way, a contact-based dialect is created by inadequate acquisition of the target language. Within the generative tradition, researchers have also noticed that people tend to be less conscious of syntax than of phonology. [note 5] Below we will try to be more specific than Van Coetsem.

Contextually determined flection is automatic and subconscious, involving a relation between two nodes in the syntactic tree. From the minimalist point of view, we can formalise the contrast by using the term tree-extension. Instead of flection, we can also speak of checking.

Contextual checking: necessitates tree-extension (move and join) to check off semantic features
Inherent checking: phonological recognition, both regular and exceptional

Note that a specific ending may involve a mixture of contextual and inherent checking, in case after tree-extension look-up in the lexicon is needed in order to determine phonological shape. We will now make the following claim about imperfect second language acquisition:

Checking effects in language contact
Imperfect second language acquisition involves the projection of contextual checking mechanisms of the first language into the contact dialect provided that the inherent checking mechanisms projected from the second language allows this.

Note that we are limiting ourselves to cases of language contact in which the first language or mother tongue is also the receding language, socio-historically speaking, and in which the second language is also the advancing language. Thus we keep the sociological factors constant in order to be able to get a clear view of the linguistic interaction. Kaufman & Thomason claimed that there is no linguistic system underlying language contact but they did not keep the sociological context fixed. A close look at Kaufman & Thomason would reveal that certain linguistic types of contact are systematically related to certain sociological states of affairs. In this paper we study the case where an advancing second language replaces a receding first language. We will show that the proposed checking effects in language contact allow us to predict the actual shape of contact dialects.

We will first introduce the historical background of the Frisian-Dutch and Frisian-Saxon contact dialects and then go on to analyse some of their linguistic properties within the framework proposed above. We predict that the contact dialect will roughly exhibit the inherent flection of Dutch and the contextual flection of Frisian.

3. Frisian Contact dialects

3.1. Three Frisian-Dutch contact-dialects

3.1.1. West-Frisian

Nowadays, West-Frisian is a countryside dialect spoken in the North of the province of North Holland. It probably developed from being a Frisian dialect to being a Frisian-based contact dialect after the military defeat of the West-Frisians in 1253. The tax system of the County of Holland was imposed and Dutch naturally became a status language for all West-Frisians who purchased a chareer in army, trade or burocracy. Furthermore, the expansion of the Zuiderzee (nowadays IJsselmeer) in the preceding centuries would naturally have led to closer economic contacts of the West-Frisians with the County of Holland, and less economic contacts with the Frisians living on the other side of the water.

The data presented below come from books written in the West-Frisian around the middle of the twentieth century (Butter 1944). An all-round grammatical investigation of the similarities between Frisian and West-Frisian was conducted in Hoekstra (1994a, 1994b), unveiling many morpho-syntactic similarities between Frisian and West-Frisian. Independent confirmation of the findings reported here comes from texts from the end of the nineteenth century presented in the dialect survey of Leopold & Leopold (1882).

3.1.2. Town Frisian

Town Frisian (see Fokkema 1937 for a grammatical description) came into existence in the sixteenth and seventeenth centuries as a status dialect when speakers of Frisian attempted to speak Dutch under the influence of the prestige which Dutch had acquired at that time (Van Bree 1997, but cf. Jonkman 1993 for a different view). Its status decreased in the course of time, and now it has the same low prestige which most city dialects tend to have. However, it is still spoken by a part of the city population.

3.1.3. Bildt

Bildts is a Frisian-based contact dialect spoken by approximately 10,000 speakers in the North of the province Fryslân (Buwalda 1963, who also gives some grammatical information). The dialect came into existence after land had been reclaimed from the sea at the beginning of the sixteenth century. The land was subsequently settled by farmers from South and North Holland. Subsequently, there was large migration from the surrounding Frisian area.

3.2. A Frisian-Saxon contact dialects: Groningen

It is uncontroversial that Frisian was once spoken in Groningen, as is evident from the fact that documents drawn up in Old Frisian have been found there. Furthermore, the dialects of Groningen, especially those spoken in the West and the North of the province (Westerkwartier and Hogeland) are, morphosyntactically speaking, very similar to Frisian (Hoekstra 1998). Like the previous cases we discussed, the syntax of Groningen has many similarities with Frisian, but the phonology has not.

4. Linguistic properties and discussion

4.1. Inherent checking phenomena from Frisian which got eliminated from the contact dialects

In this section, we will present an overview of the facts of two inherent checking phenomena in the contact dialects: the case of the conjugation of JE-verbs and the irregular pasts and perfects of strong verbs. In both cases, it will turn out that the Frisian forms did not survive into the contact dialects.

4.1.1. The case of the conjugation of JE-verbs

Frisian has two verb classes judging from the infinitives, those having an ending in -E(N) and those having an ending in -JE(N). Their conjugation in present and past tense, and the shape of the participle, is given below (Tiersma 1985:68ff) [note 6]:

(3) conjugation of rûke "smell" (-JE) and helje "fetch" (+JE)
present (-JE) (+JE)
1s rûk helje
2s rûkst hellest
3s rûkt hellet
pl rûke helje
1s rûkte helle
2s rûktest hellest
3s rûkte helle
pl rûkten hellen
past participle
rûkt helle

Interestingly, neither Dutch nor Saxon has the -JE verbs (nor the concomitant conjugation). What happened in the contact dialects? Neither the Dutch contact dialects (WW-Frisian, Bildts, Town Frisian) nor the Saxon ones (the Groningen dialects) have -JE verbs. I use in the table the word declension for a deviant conjugation class.

(4) JE-declension?
Dutch no
West Frisian no
Town Frisian no
Bildts no
Frisian yes
Groningen no
Saxon no

Now, the JE-flection itself is a class-feature. Hence it is an instance of inherent flection: no element within the sentence selects a JE-verb or a non JE-verb, this is given in the lexicon. Language-contact theory correctly predicts that this feature involving inherent flection of the receding first language will not be projected into the contact dialect.

4.1.2. The irregular past and perfect of strong verbs

Cor van Bree (1994) conducted an in-depth study of strong verbs in Town Frisian. [note 7] He concluded that the past and perfect of strong verbs in Town Frisian was very much like Dutch and very much unlike Frisian. If we look at the other contact dialects, we note that the past and perfect forms are not reminiscent of Frisian. In the case of Town Frisian, Bildts and West Frisian, they look more like Dutch. In the case of Groningen, the irregular verb forms look very much like the adjacent Saxon dialects.

(5) Strong pasts and perfects look like Frisian?
Dutch no
West Frisian no
Town Frisian no
Bildts no
Frisian yes
Groningen no
Saxon no

Some illustrative examples from Town Frisian (Van der Burg 1991), Bildts (Buwalda et al. 1996) and Dutch versus Frisian are given below:

Town Frisian biede - boad - boaden
Bildts biede - boad - boaden
Dutch biede - bood - geboden
Frisian biede - bea - bean

Town Frisian breke - brak - broken
Bildts breke - brak - broken
Dutch breken - brak - gebroken
Frisian brekke - briek / bruts - brutsen

The irregular past and perfects are listed in the lexicon as idiosyncratic properties of the verbs involved. Hence we are dealing with inherent flection. As such, it is correctly predicted that the irregular flection of Frisian will not be projected in the contact dialects. Instead, the contact dialects take over the forms of the second language.

4.2. Contextual checking phenomena from Frisian which survived in the contact dialects

In this section we will present an overview of three contextual checking phenomena in the contact dialects. Two of these involve leftward movement in the Kaynian framework. The prediction for leftward movement is that those phenomena will survive from Frisian into the contact dialects, since they involve contextual checking.

4.2.1. Ending of 2 SG

Verbs in Dutch have a -T in the second person singular in the present tense, and in inversion the -T is absent. In the past tense, there is no inflectional ending. In Frisian, 2SG verbs end in -ST in present and past tense alike:

(7) 2SG in Dutch and Frisian for the verb "come"
Dutch Frisian
present je komt / kom je (do) komst / komst (o)
past je kwam / kwam je (do) kaamst / kaamst (o)

Interestingly, the contact dialects all pattern with Frisian, with the exception of West-Frisian:

(8) 2SG verb ending is -ST?
Dutch no
West Frisian no
Town Frisian yes
Bildts yes
Frisian yes
Groningen yes
Saxon yes

Some examples of -ST ending from Town Frisian, Bildts and Frisian versus Dutch are given below (the Groningen case is trivial, since Saxon dialects have a -S(T) ending like Frisian anyhow, details aside):

(9) Example of -ST ending in equivalents of "have"
Town Frisian dou hest dou hast
Bildts dou hest dou hast / haddest
Frisian do hest do hiest
Dutch je hebt je had

The -ST suffix is a case of contextual flection, since it involves a relation between the verb and the subject. The flection is insensitive to lexical factors so we are dealing with contextual flection exclusively. We now expect that the -ST ending will be projected in the grammar of the contact dialect.This is what happens, since there is nothing in the second language to prevent this from happening. Let me explicate this.Dutch verbs have a -T in the second person singular present. The Frisian ending also ends in -T, hence there is no clash. Where Dutch does not have -T, there is no problem either; the Frisian -ST forms are comparable to Dutch verbs having a stem ending in -ST.My analysis seems to rely on a distinction between the creation of inflected forms and the recognition of inflected forms, the latter being a more superficial process. Language contact typically creates new contact dialects because of the mismatch between the creation of words and the recognition of words, put differently, because of the mismatch between grammar and parser. [note 8] Hence the survival of -ST into the contact dialects is exactly what we expect. Unexplained is the lack of -ST in West-Frisian. We can only suggest that -ST got lost as a later development, though this suggestion is void in the absence of historical evidence confirming or disconfirming the hypothesis.

4.2.2. The naked verb-first construction (Imperativus-pro-Infinitivo or IPI)

The Imperative-pro-Infinitive construction is a construction which, in spite of its name, has as its most characteristic property that the verb, a bare verb form or an infinitive, appears at the beginning of the sentence:

(10) Frisian
Ik bin net fan doel [en praat der mei him oer]
I am net of purpose and talk it with him about]
"I do not intend to talk with him about it"

Here the verb praat "talk" of the second conjunct appears at the beginning of the clause, instead of at the end. Normally, the subclause would have the verb at the end:

(11) Frisian
Ik bin net fan doel [der mei him oer te praten]
I am not of purpose[it with him about to talk]
"I do not intend to talk with him about it"

In older Frisian, even at the beginning of this century, the verb appeared as an infinitive at the beginning of the sentence. The development towards a bare verb form is very recent. The IPI-construction, with an infinitive, also occur in mainly northern Dutch dialects, but not in the Standard Dutch, neither written nor spoken. This construction is also found in Bildts, Town-Frisian and Groningen dialects, but not in W-Frisian, as shown below:

(12) IPI-construction attested?
Dutch no
West Frisian no
Town Frisian yes
Bildts yes
Frisian yes
Groningen yes
Saxon yes

Examples from Town Frisian and Bildts are given in (13-14):

(13) Town Frisian
Súst wel wizer weze en loop dy meid achterna
you would PRT wiser be and walk that girl after
"You wouldn't be so foolish as to woo that girl."

(14) Bildts
dou mâgst d'r wel om dinke en doen soks nooit weer
you may there PRT about think en do such a thing never again
"You should take care never to do such a thing again."

The absence of the construction in W-Frisian may be taken as an indication that the construction is not an ancient one. It also occurs in Frisian Dutch. Its presence in the Dutch of educated speakers from the province may be taken as further evidence that it is easily tranferred from Frisian to Dutch in language contact.

Movement is treated in generative grammar as in instance of contextual flection. In the IPI-construction, the verb surfaces next to the complementiser EN under the influence of that complementiser. It is not a lexical property of the verb that it surfaces in that position; this occurs to check of semantic features. Given the contextual nature of movement, we correctly predicts that the grammar of the contact dialects exhibit the IPI-construction, seeing furthermore that no lexical or phonological property in the grammar of Dutch blocks this. Again we cannot explain why West-Frisian behaves differently in this respect.

4.2.3. Verb clustering

The same argument can be made for verb clusters, which are head-final in Frisian and in the Frisian contact dialects but not in Dutch. Verb clustering is an instance of movement, and therefore we expect that Frisian word order will be projected in the contact dialects. This turns out to be correct. [note 9]

4.3. Contextual and inherent checking: the case of infinitival endings

I will briefly summarise here the results of research reported elsewhere more fully (Hoekstra MS).

4.3.1. Distribution of the two infinitives in Frisian

One of the most noticeable characterics of the Frisian language family is the presence of two infinitival endings, as was already noted in Halbertsma (1865). This is not only a phonological matter but also a syntactic one since the distribution of each ending is syntactically determined. The two endings are -E and -EN. The latter is usually but not obligatorily pronounced as a syllabic nasal. The distribution of the two infinitives in Frisian is given below

(15) The infinitive in -E is found

A. As a complement to modal auxiliaries
Ik sil him opskiljE
I shall him up-phone
"I will phone him up."

B. As a complement to the causative verb litte "let"
Lit him mar gewurdE
let him just become
"Just let him be."

C. As a complement to the auxiliary for preposed verbal complements dwaan "do"
Boeken lêzE docht er komselden
books read does he rarely
"Read books, he does rarely."

D. In unselected infinitival sentences
Ik boeken lêzE?
I books read
"Me read books?"

(16) The infinitive in -EN is found:

A. As a complement to verbs of perception such as hearre "hear"
Ik hear Jarich al laitsjEN
I hear Jarich already laugh
"I already hear Jarich laugh."

B. As a complement to the verb gean "go"
Ik gean sittEN / steaN / lizzEN / oan 'e rekstôk hingjEN
I go sit / stand / lie / on the bar hang
"I'll sit down / I'll stand up / I'll lie down / I'll hang from the bar."

C. As a complement to the verb bliuwe "stay"
Ik bliuw sittEN / steaN / lizzEN / oan 'e rekstôk hingjEN
I remain sit / stand / lie / on the bar hang
"I'll remain sitting / standing / lying / hanging from the bar."

D. As a complement tothe verb komme "come" plus a particle of directional movement.
Dêr komt Jan oan rinnEN
there comes Jan along walk
"John comes walking along."

E. As a nominal complement, e.g. to various determiners such as it "it", dat "that".
It rinnEN docht my deugd
the walking does me virtue
"To walk is good for me."

F. As a complement to the infinitival marker te "to".
Om te winnEN!
in order to win
"In order to win."

G. As complement to the verb hawwe "have"
Hy hat it boek op tafel lizzEN
he has the book on table lie
"He has the book lying on the table."

4.3.2. Table of the distribution of the infinitives in the contact dialects

The following table gives the distribution of the infinitives in -E and -EN in the contact dialects as compared with Frisian and Saxon. Note that Dutch exhibits arbitrary variation between -E and -EN as infinitival ending.

(17) Distribution of infinitival endings in contact dialects in syntactic contexts
contexts Frisian West Frisian Town Frisian Bildts Groningen Saxon
(15) -E -E -E -E -N -N
(16) -EN -EN -EN -EN -N -N

Frisian and Sxon have been added for comparison.

4.3.3. Survival of the Frisian system in the Dutch contact dialects and its death of the Frisian system in the Saxon contact dialects

Consider first the case of Dutch-Frisian contact dialects as they developed. There is no phonological barrier for interpreting the Frisian endings as Dutch,as the latter exhibited arbitrary phonological variantion in its infinitival endings -E and -EN. Thus Frisian speakers could impose the syntactic conditioning of the choice between -E and -EN on the contact dialect, an instance of contextual checking (note that Dutch does not have syntactic conditioning of -E and -EN). Hence we find the Frisian system of infinitives in the Dutch-Frisian contact dialects: West Frisian, Town Frisian and Bildts. Consider next the case of Saxon-Frisian contact dialects. Saxon required the -EN, Frisian required either -E or -EN. The Frisian -E now no longer can survive, since it violates the Saxon phonological requirement that -EN be present. Therefore, the -E gets lost and only -EN survives. Under this view, speakers recognise a phonological requirement in the second language, Saxon, such that infinitives always end in -N. Thus inherent checking of the infinitival ending for -N blocked the imposition of the -E ending in the Saxon contact dialects.

5. Conclusion

The advantage of language contact theory is, first, that it is consistent with what we know of history. History offers many known examples of speakers of one language adopting a second language which, imperfectly learned and hence influenced by the dying mother tongue, changed into a first language. That is, for example, how Latin spread into France at the cost of Celtic, changing into French in the process. On a smaller scale, the same process must have taken place at the level of dialects. We have attempted to spell out the mechanism of the creation of new contact dialects under the influence of language contact. It seems as if the grammar of the mother tongue survives into the contact dialect if it can superficially look like the second language. Thus the syntactic distribution of infinitives in Frisian survived into the contact dialects involving Dutch because the endings are phonologically similar to what is found in Dutch. By the same line of reasoning, the Frisian infinitives did not survive into contact dialects involving Saxon. The same applies to the -ST ending, which survived into Dutch because it is superficially similar to the Dutch system having either -FF ZERO. Word order phenomena survive trivially since they do not involve phonological or lexical conditions in the second language; they pattern with contextual flection. Our account implies that inadequate second language learning primarily targets the phono-lexical component. Hence irregular morphology is not projected from the mother tongue into the contact dialect. We have presented a complex typological body of facts involving phenomena from contact dialects, which not only serve as a test for the theory proposed here but which may also serve as a test for theories proposed by others.


1. I would like to thank the participants of the 15th Workshop on Comparative Germanic Syntax (Groningen, 26 - 27 May 2000) for comments and discussion.

2. The study of second language acquisition is thus relevant for explaining why a contact dialect has a specific shape and not another shape, seeing that the contact dialect came into existence as an example of imperfect second language acquisition. Put differently, second language acquisition is relevant for historical linguistics and dialectology.

3. The international community refers as "West-Frisian" to what is referred to as "Frisian" within The Netherlands, that is, the official second language of the province of Fryslân. Within the Netherlands, the term "West-Frisian" is reserved for the dialect spoken in West-Friesland, in the North of the province of North Holland, that is, on the West side of the IJsselmeer. In this article, I will reserve the term West-Frisian for that dialect]

4.The recession of Frisian in the province of Groningen may be due to the advance of the Saxon dialect of Drente or to the advance of the Plattdeutsch dialect of adjacent Germany, or both. Plattdeutsch and Drente are closely related Saxon dialects whose influence may well have combined to oust Frisian from Groningen. Many (rich) people from Drente emigrated to Groningen [Naarding 1961, and when the East of the province was turned into fertile land, there was migration from adjacent Germany, see Schmitt 1942.

5. Eric Reuland proposed to explain differences in the behaviour of anaphors in this vein. He related their distribution to PF and LF licensing. Type of licensing depended on the morphophonological shape, PF-licensing being associated with conscious effort and LF-licensing with unconscious application.

6. Johannes Hoekstra (1993) analyses the process of linguistic change involving JE-verbs within Frisian. Contrary to e.g. Kaufman & Thomason (1988), he claims that in spite of the large heterogenuity of the material linguistic systematicity can nevertheless be observed. This bears out our earlier claim that linguistic systematicity can only be observed if the sociological context is kept constant.

7. Van Bree (1994, 1997) analysed Town Frisian within the framework of Van Coetsem, and reached the conclusion taken over and defended here: Town Frisian arose as a contact dialect with Frisian as a mother tongue.

8. The actual mental situation is more complicated: we have two grammars, a Frisian and a Dutch one, and two parsers, a Frisian and a Dutch one. I am implying that Frisian grammar is checked off by a Dutch parser. The contact dialect is fed by the grammar of the first language as filtered by the parser of the second. The parser of the second language is much more developed than the grammar of the second language, since comprehension is better developed than production when people do not speak a language perfectly yet. This fact is also well-known from first language acquisition: children's passive knowledge is greater than their active knowledge.

9. It has been objected, correctly, by Rolf Bremmer (1997) that Middle Frisian did not have verb-final order. Note, however, this applies to written Middle Frisian. If spoken Middle Frisian did not have verb-final order either, then it is accidental that we nowadays find verb-final order in the area where Frisian was once spoken. On the other hand, we know that written language may be completely different from spoken language. My guess is therefore that Middle Frisian shows head-initial orders under the influence of the Dutch written standard.


Bree, C. van (1994) "Het probleem van het ontstaan van het 'Stadsfries' in verband met nieuwe talen in contact-theorieën". In Acta Universitatis Wratislaviensis (no 1651), Handelingen Regionaal Colloquium Neerlandicum.

Bree, C. van (1997) "Die Syntax des Stadtfriesischen im Vergleich mit Niederländisch und Friesisch". In V.F. Faltings, A.G. Walker & O. Wilts (eds) Friesische Studien 3 (North-Western European Language Evolution suppl. vol. 18, 1-48.

Bremmer, R. (1997) Het ontstaan van het Fries en het Hollands. In P.H. Breuker & R. Bremmer (eds) Negen eeuwen Friesland-Holland. Geschiedenis van een haat-liefde verhouding. Zutphen.

Burg, A.C.B. van der (1991) Woardeboek fan ut Leewarders. Fryske Akademy, Ljouwert.

Butter, F. (1944) Trienke Boôd. De roman van een boeredochter. West-Friesland, Hoorn.

Buwalda, H. S. (1963) Hoe skrive wy 't in 't Bildts? 'n Handlaiding foar de spelling en inkele dingen út 'e spraakkûnst. Drukkerij Van Leer & De Jong, St.-Annaparochie.

Buwalda, H.S., S.H. Buwalda and A.C.B. van der Burg (1996) Woordeboek fan 't Bildts (en list fan toponimen). Fryske Akademy, Ljouwert.

Coetsem, F. van (1988) Loan Phonology and the Two Transfer Types in Language Contact. Foris, Dordrecht.

Fokkema, K. (1937) Het Stadsfries; een bijdrage tot de geschiedenis en de grammatica van het dialect van Leeuwarden, Assen.

Fokkema, K. (1948) De Liwadder an 't wood. Zeven eeuwen taalgebruik in Leeuwarden. Van Gorcum, Assen.

Halbertsma, J. (1865) [Besprek fan "Die Nordfriesische Sprache nach der Mooringer Mundart" troch Bende Bendsen, Brill, Leiden, 1860)]. De Vrije Fries 10, 345-438.

Hoekstra, E. (1994a) Positie- en Bewegingsaspect bij Selectie van de Infinitief op -E of -EN in het Westfries en het Fries. Taal en Tongval 46, 66-73.

Hoekstra, E. (1994b) "Oer de oerienkomst tusken de dialekten fan Noard-Hollân en it Frysk". Yn Ph.H. Breuker, S. Dyk, D. Gorter, L.G. Jansma en W. Visser (red.) Philologia Frisica anno 1993. Fryske Akademy, Ljouwert, 81-103.

Hoekstra, E. (1998) "Oer de oerienkomst tusken de dialekten fan Grinslânsk en it Frysk." In Ph. Breuker, S. Dyk, L. Jansma, W. Visser & J. Ytsma (redaksje) Philologia Frisica anno 1996. Fryske Akademy, Ljouwert, 117-137.

Hoekstra, E. (Ms) "The case of the two infinitives, language contact theory and the question of Frisian substrate in the Netherlands." Fryske Akademy, Ljouwert (Leeuwarden).

Hoekstra, J. (1992) "Fering tu-infinitives, North Sea Germanic syntax and Universal Grammar". Yn: V. Faltings, A. Walker & O. Wilts (red.) Friesische Studien I, 99-142. Odense University Press, Odense [=NOWELE Supplement vol. 8].

Hoekstra, Joh. (1993) It feroaringsproses by JE-tiidwurden. Tydskrift foar Fryske Taalkunde 8, 43-51.

Jonkman, R. (1993) "It Leewarders. In taalsosjologysk ûndersyk nei it Stêdsk yn ferhâlding ta it Nederlânsk en it Frysk." Fryske Akademy, Ljouwert.

Laan, K. ter (1953) Proeve van een Groninger Spraakkunst. Van der Veen, Winschoten.

Leopold, J.A. & L. Leopold (1882) Van de Schelde tot de Weichsel. Nederduise dialecten in dicht en ondicht (3 dln).Wolters, Groningen.

Naarding, J. (1961) "Stad en Ommelanden". In K. Heeroma en J. Naarding (red.) De Ontfriesing van Groningen. J.K. Hertz, Zuidlaren, 45-62.

Reker, S. (1991) "Vormleer". Groninger Grammatica. Staalboek, Veendam.

Schmitt, L.E. (1942) "Die Stadt Groningen und die Mundarten zwischen Laubach und Weser". Zeitschrift für Mundartforschung 18, 134-170.

Schönfeld, M. (1970) Historische Grammatica van het Nederlands. Verzorgd door A. van Loey. W.J. Thieme, Zutphen.

Tiersma, P.M. (1985) Frisian Reference Grammar. Foris, Dordrecht.

Visser, W. (1988) "Ta de nominale ynfinityf yn it Frysk". Philologia Frisica anno 1988. Ljouwert (1989), 51-72.

Walker, A. (1995) "The Dialects of Modern German". In C. Russ (ed.) The Dialects of Modern German. Routledge, London.