From 2012 around 5,000 foreign fighters from European countries went to the Levant to fight. Six years later, an estimated fifteen percent has died in battle. Others are still in the Middle East, imprisoned or perhaps on the move to centers of conflict elsewhere in the world, now that the terrorist groups are in the defense. But others return to their home country.
This phenomenon of homecoming foreign fighters somehow surprised European countries and their sophisticated policy makers. Criminal legislation reforms were rather reactive and ad hoc. As if everyone expected all of them would be killed in battle anyway. How is this possible? Especially for countries bordering the Wadden Sea. This region has after all a history piled-up with foreign fighters participating in foreign forces. Whether it was for reasons of faith or for booty and glory or, in practice, a toxic combination of these incentives.
Oh, you did not know? Essential you finish reading this blog post.
If we leave the Frisian mercenaries in the Roman imperial army aside (read our blog post Frisian mercenaries in the Roman Army to learn more about these fighters), there have been two major waves of homegrown foreign fighters. The first wave was during the Viking Age, roughly between 800 and 1000. This was followed by a second one during the Crusading Period, roughly between 1100 and 1300. In our blog post Terrorist Fighters from the Wadden Sea we already elaborated on the Frisian crusaders, and the society-undermining effects caused by the return of these holy fighters.
In this blog post we will zoom into the return of Frisian fighters who took part in ransacking Viking war bands, and how the process of homecoming of these guys was a social reality, and how it was regulated. We will illustrate that both Germany and the Netherlands have a long legal tradition of a thousand years how to deal with homecoming foreign fighters.
It is difficult to estimate how many men (and women?) of Frisia took part in raids of the Vikings across Europe and beyond. The Frisians, however, were not unique and other peoples and tribes also participated in the raids of the Norsemen. It were probably quite relevant numbers that came from Frisia. For example, in the year 855 an army of pagans, of Dani et Frisones ‘Danes and Frisians’ landed on the island of Sheppey eastern England, according to the Annales Lindisfarneses. Furthermore, a few years after the attack at the island of Sheppey, it was from the River Scheldt estuary, part of Frisia territory, that Ubbe the Frisian departed with his army of Scaldingi ‘Scheldt Vikings’ to invade England. Ubbe, also Ubbi fríski, is one of the three founding commanders of the legendary fearsome Great Heathen Army. This same Ubbe is said to have led, together with the leaders Inguar and Halfdene, the raid on Sheppey.
Who was Ubbe?
Often it is assumed that Ubbe is Danish, since he is a son of Ragnarr Loðbrók according to legends. However, we can safely assume Ragnarr was non-historical (IJssennagger 2017), which makes Ragnarr irrelevant for proof concerning Ubbe’s ‘nationality’. Part of the legend is that Ubbe had a Frisian mother.
The name Ubbe is a Frisian first name till this day and derives from the first name Obe. Old Frisian legends speak of the third prince of Frisia named Ubbo I. He ruled over Frisia between 151-71 BC, and was a grandson of Prince Friso, who founded Frisia. Ubbo I is also the founder of the city of Cologne. The fourth duke of Frisia was Ubbo II. He ruled over Frisia between AD 240-299, according to old non-historical legends again, of course. Another Ubbo is the high-medieval local ruler Ubbo Habbena from Aurich, Ostfriesland.
There are scholars who suggest the name Ubbe is, in fact, Old-Norse and derives from Úlfr. Thus adding an ‘l’ to the name. According to this theory Ubbe and the Viking warlord Rodulf (Rod Ulf, meaning ‘praise wolf’) were one an the same person, and Ubbe was born and raised at Walcheren, Frisia (Lewis 2018). To complicate things even more, at the mouth of the River Old Rhine, the Frisian settlement Hrothaluashem ‘Rodulfsheim’ exsisted, meaining ‘House of Rodulf’. Today it is known as Rijnsburg. Hrothaluashem is considered to be part of an early-medieval elite central-place-complex, as can be found in southern Scandinavia as well. Concerning more background on CPC’s, check out our post Tolkien pleaded in favor of King Finn.
Or, should we keep it simple? Firstly, Ubbe is, as said, a typical Frisian first name. Secondly, Ubbe was not nicknamed ‘the Frisian’ without reason. Thirdly, he did not command the Scaldingi, the Scheldt Vikings, i.e. warriors from the River Scheldt ín Frisia, for no reason either. Fourthly, ‘foreigners’ participating in Viking raids was common. So, Ubbe is just a Frisian. And who knows, the distinction between raiding Frisians and Danes was a fluid one, and of which Ubbe might have been a typical example.
That ‘Viking’ was also a job description besides belonging to an ethnic, Scandinavian group, is confirmed in recent genetic research (Margaryan 2020). Genetic samples of ‘Viking burials’ from among other the British Isles, to Italy, Russia and the Ukraine show that graves typified as Vikings were, in fact, were sometimes locals or non-Scandinavians. Also, albeit limited cases, that so-called Viking warriors buried in Scandinavia turned out to be Saami. Unfortunately, no old genetic samples from the southern North Sea coast (i.e. Frisia) have been included in this recent research, maybe too close and overlooked?
In Yorkshire is the place name Frizinghall ‘Hall of Frisians’. This name derives from Frisian settlers. Of course, we like to speculate this was where Ubbe had his hall. Frizinghall belongs with about twenty other place-names to settlements that can be etymologically attributed to Frisian settlers in Britain. Moreover, most of these place names are located in the former Danelaw, giving away the time they settled there. Were it Vikings too? Read also our blog post Have a Frisians Cocktail to learn more about Frisian place-names in Britain.
If interested to know more about this chap Ubbe and his Great Heathen Army read, only during daylight, our post Island the Walcheren: once Sodom and Gomorrah of the North Sea.
For now, we leave all the sea fog surrounding Ubbe behind us, and return to political Frisia. Early-medieval Frisia, stretching during the Viking Age between the mouth of the River Scheldt in southwest of the Netherlands, and the mouth of the River Weser in the northwest of Germany, bordering with the land of the Danes and of the Saxons. Roughly 500 kilometers of almost impenetrable coast. Geographically this sandy, muddy and peaty coast was centrally located between the Dena lagunema ‘Danelaw’ on the British isles to the west, and Denmark plus southern Norway and Sweden to the east and northeast.
The influence of the Vikings, whether under final authority of the Frankish kingdoms or not, was even very direct. In the ninth century Viking warlords like the renowned Rorik of Dorestad, Hemming Halfdánsson, Rodulf, Harald Klak and Godfrid the Sea-King governed big parts of Frisia. These areas were: the central river-lands with the most lucrative trade emporium of northwest Europe namely Dorestat, the coastal zone along the North Sea named Kinhem or Kinnlimasiða in Old-Norwegian (present-day Kennemerland in province Noord Holland), and the estuary of the River Scheldt including the Walachria Island (present-day Walcheren in province Zeeland). All located in what is part of the Netherlands today. Read also our post The Abbey of Egmond and the Rise of the Gerulfing Dynasty for more background about these Danish warlords ruling (West) Frisia.
Besides West and Mid Frisia, also East Frisia was ruled by a Danish warlord. It was the Viking earl warlord Harald Klak who ruled on behalf of the Franks over the pagus (district) Rüstringen in the part of former Frisia in the northwest of Germany. From there, he controlled the mouths of the rivers Weser and Jade. That was in the second quarter of the ninth century. The Battle of Norditi, in the area Norderland in region Ostfriesland, in 884 was also a consequence of (semi) permanent presence of Norsemen. The battle was won by the Frisians, and it took the lives of a staggering 10,377 Danes. Read our blog post A Theelacht. What a great idea! Long-term presence of the Norsemen is also presumed at the (former) islands Texla (present-day island Texel) and Wiron (present-day Wieringen) in the northwest of the Netherlands. More about island Wieringen later.
Concerning (semi-) permanent presence of Vikings in Frisia, a fascinating example is given in the ninth-century Annales Fuldenses of a Norseman living among the Frisians and helping them out when a Viking raiding party attacks his host country. Read our post Frisia, a Viking graveyard to read the whole account. Furthermore, the presence of the aforementioned Ubba the Frisian and the Scaldingi chapter in modern province Zeeland, is also relevant in this context. Lastly, distribution patterns of the so-called imitation gold solidi (i.e. coins) indicate (semi-) permanent presence of Vikings in Frisia too, especially in current provinces Friesland and Groningen. These coins probably have been minted by Vikings instead of Frisians, as was assumed (Coupland 2016).
The Frisian and Danish sea tribes were also culturally related. Frisia had been converted to Christianity recently but before that shared the same heathen believe as their northern cousins for centuries. Yes, they might even have identified themselves with the Norsemen. Despite the fact the Franks incorporated parts of Frisia into their kingdoms over the course of the eighth century, and despite the many Anglo-Saxon monks from the Irish monastery Rath Melsigi who tried to evangelize Frisia, the Frisians living at the outer rim of their motherland might not have been fully pacified and certainly not baptized yet during the Early Middle Ages, and therefore they kept interacting with their pagan neighbors as ever before.
Alle Fresa er north herden ouer thet hef anda grimma herna and thet al hethen was, ther Fresena was.All Frisians once belonged to the north over the sea to the terrible corner and all were heathen, who were Frisians (Old-Frisian Emsinger Law).
These texts are from the High Middle Ages. By then the Frisians were indeed a people that only recently had changed their allegiance. From the heathen, barbaric north to the Christian, civilized south. This is symbolized by the tribute or tax they had to pay, namely from the clipskelde to the huslotha. The word clipskelde is composed of the Old-East-Frisian word clippa/klippa, meaning ‘to clink’, and the word skelde meaning ‘debt’. So, a clinking-debt. Old-Frisian law prescribed that the pennies to be paid had to be this heavy that “ma him moeghe hera clinna jn ene lewen wr nioghen fecke huses” (meaining: one can hear them clink in a scale over a distance of nine house lots). The word huslotha is composed of the word hus, meaning ‘house’, and the word lotha. Of the latter it is a bit unsure what it means but it might mean ‘part’ or, indeed, a lot or plot of land. The clipskelde was the tribute paid to the Norsemen/Danes for loyalty to an overlord. The huslotha was a tribute paid to the Franks.
Thet wi Frisa suther nigi and clipskelde urtege and wrthe tha suthera kininge hanzoch and heroch alles riuchte tinzes and togetha and huslotha urgulde, bi asega dome and bi lioda londriuchte, al with thet wi er north herdon Redbate tha infrethmonne, al thet Frisona was.That we Frisians subjected ourselves to the south and clipskelde [tribute] refused and became subordinate and obedient to the southern king, regarding all rightful tenths [kind of tax] and paid huslotha [house tax], according to the asega’s [law expert] judgement and according to the people’s land-law, because we belonged to [King] Redbad the unpieceful-man, all that was Frisian.
Furthermore, both (i.e. the Scandinavians and the Frisians) were heavily entangled in the rich supra-regional trade since long. All over southern Scandinavia at important trading ports, Frisian trade colonies and Frisian guilds were established. The get an idea about the magnitude of the Frisian free-trade read our blog post Porcupines bore U.S. bucks.
Participation of the Frisians in the Viking war bands could be voluntarily and could be involuntarily. During raids the noerdtscha diuelen (Old-Frisian for ‘northern devils’) could take captives. Sometimes young children, sometimes adults. They could be sold as slaves back home, or sold somewhere else for a fair price. They also could be bought free by their relatives, which still meant a profit for the cunning Vikings. Lastly, captives could be forced to participate in plundering, killing and raping during raids. The focus of this blog post.
Saga of the Headstrong Frisian
This saga, of the Viking Age, is about a North-Frisian, from the Wadden Sea island Balkum in Nordfriesland. Balkum was located west of island Föhr. The Headstrong and especially heathen Frisian, participated in Viking raids. When one day he returns from one his raiding trips, his island has been swallowed by the sea. Although this was already quite a blow for him, moreover, all of his kin and friends were converted by the Catholic church in the meantime too. This was really more than he could bare. From the sacrificial stone, that was at Balkum, he threw himself into the sea and drowned.
Some of the captives were able to flee or were bought free at a later time, after which they returned to their village and to their family estate in Frisia. The numbers of homecoming foreign fighters were that significant that it was regulated by law. Again, an indication the Frisians manning Viking longships too.
The Old-Frisian codices or law books of the fourteenth and fifteenth centuries, still contained articles or clauses concerning homecoming Frisians from Viking captivity. Some of these codices have been built up over the centuries, traceable from ca. 1000. The medieval Old-Frisian law books therefore contain different names for the word viking. These are: witzing, witzeng, wising and witzend and originate from the Old-English word wicing, meaning pirate. Similar, the origin of the word ‘saxon’ also means pirate (Springer 2003). Read our blog post Have a Frisians Cocktail on this topic of the origin of Saxons too.
Thus, saxons and vikings were terms to indicate a ‘profession’ if you like and, at first instance, not to denote a people or tribe. A different etymological explanation is that the word viking derives from the Old-Swedish verb vika or Old-Norse vikja meaning ‘to change rowers’ and ‘to give way’. Comparable to the modern Mid-Frisian verb wykje. So, ‘to give way on a rowing bench for a rested rower’, therefore vika and ‘to viking’ meaning ‘sea voyage with rowers changing’ (Heide 2005).
Below the clauses of two law books concerning the return of Frisian fighters, namely the Fivelgo Manuscript and the First Rüstringer Codex. Fivelgo is a shire in present-day province of Groningen in the Netherlands and Rüstringen is a shire in present-day region Ostfriesland in Germany. The First Rüstringer Codex, or R1 in jargon of historians, dates from ca. 1300. The Fivelgo Manuscript, or F in the same jargon, dates from ca. 1450. Both texts concern the Twenty-four Land Laws.
Thit is thet twintegoste londriucht: Sa hwersa Northman an thet lond hlapath, and hia enne mon fath and bindath and ut of londe ledath, and eft withir to londe brangath and hini therto thwingath, thet hi hus barne and wif nedgie and man sle and goishus barne and hwetsa hi to lethe dwa mi, alsa hi thenne vndfliuch ieftha lesed werth, and withir to londe kumth and to liodon sinon, and hi mugi bikanna brother and swester and londethele and erue and sinera aldera hof and hus, sa fari hi oua sin ein erue uter liodskelde. Sa willath him tha liode thing toseka and sinne opawerpa thruch thet grate morth, ther hi er mith tha witsingon efremid heth. Sa mire thenna afara thene warf gunga and iechta mire tella; enne eth hach hi thenne opa tha heligon to swerande, thet hit al debe bi there need, alsa him sin hera bad, ther hi was liues and lethana en vnweldich mon. Sa ne thuruon him tha liode ne frana tohalda seka ni sinna, thruch thet thi frana ne machte thes fretha waria; thi skalk skolde dwa, alsa him sin hera bad, thrum thes liues willa.
This is the twentieth land law: When the Norsemen invade the land and they take a man captive and bind him and carry him off abroad and later take him back in the land and force him to burn down houses and rape women and kill men and burn down churches and whatever sort of evil he may do, and if he flees or is released and he comes back to his land and to his folk, and he recognizes his brother and sister and family estate and ground and his parents’ court and house, then he can take back his own land without payment to the folk. When his people want to charge him and accuse him of a crime because of the great murdering that he had committed with the Vikings. Then he may come before the assembly and plead guilty and confess; then he must swear on the relics that he had done everything because he was forced by his lord against whom he could not voluntarily decide over his body or life. Then neither the people nor the frana (*) can charge him as guilty or with crime, because the frana cannot secure his peace; the servant had to do what his master ordered, for his life’s sake.
(*) The frana was a functionary originally acted on secular matters on behalf of the bishop. Task of the frana was to guarantee the peace and execute legal rulings. For this the frana had the monopoly for violent action against disobedient. It was his duty to execute the legal rulings. Originally, the frana, together with the asega (literally meaning ‘law saying’, a legal expert and priest combined and the one guiding the trial) led the process of law.
Thet twinthechgiste londriucht is: jefter Northmon kumath and anne mon hendat and bunden to tha skipe brengat and hi mith himman in sine ayna londe to ene thorpe kumpt an hi ther hus barnt ande wif a need nimth ande mon slaith en hwet sa hi to ewela decht, jef hi thenna vunfliucht jefta leszed wert, sa stant hi an liudworpena ware an on tha bonnena thinge; and sprecht ma him to, thet hi alle ewela deda den hebbe, sa iecht hi the salles and queth, hi hebbe alsa den; end hi ne thor ther nen bote vmbe iewa and ac nanne frethe felle, hwant hi dede tha hwile, alsa hi en skalc was; thi schalc scolded wan, alsa him sin hera bad, thruch thes liwes willa.
The twentieth land law is: when Norsemen come and take a man captive and bring him tied up to their ships and with them he comes back in his own land in a village and he burns houses and rapes women and kills men and whatever evil he does, then he appears, when he escapes or is bought free, before a yard gathered by the people and in the banned thing (*); when he is accused for doing all these evil deeds, then he confesses all and says he has done that; and he neither needs to pay a fine nor to pay for the peace, because he did it, when he was a servant; the servant must do what his lord commands to save his life.
(*) A thing -or ting or ding- was a governing assembly of northern Germanic societies of which Frisia was part. The parliament in Iceland still is named Alþing.
Striking how similar both texts are. Even after more than a century had passed between the two. The underlying central social question was the legal certainty concerning the property of men who were taken captive by Vikings. When returning, these foreign fighters could retake possession of their former family property and land. But only under certain conditions. The first condition was that they could proof to be the rightful owner through recognizing their family and their family estate and goods. A workable alternative in a society without passports and without a central registration database of citizens. The second condition was that they made their claim within a certain period of time. The particular clauses mentioned above contain no fatale deadlines but from other Old-Frisian sources we know thirty years was a typical deadline. So, they were not in hurry to return. The third condition was that, in case they had been fighting, murdering, burning down houses, raping women, et cetera in Frisia, they had to make plausible they had done so to save their own life. In other words: they had been forced to do bad against their own kind. If all conditions were met, they could retake their possessions without paying anything to anyone.
But what was the consequence if the returnee had been killing and raping his own people out of free will? We find an answer in the Old-Frisian Hunsinger codices from the fourteenth century. It concerns not Viking war bands, though, but men who joined Saxon forces ‘with the high helmets’ and who fought against their own land Frisia. The answer: they were considered traitors.
En vrrede and hi wrreth lond and liude and hi fart inur Saxenna merka and hi uthlath thene haga helm and thene rada skeld and thene sareda riddere and hi binna Fresena merkum man sleith and burga barnd, sa ach ma hine north inna thet hef to ferane and theron te sansane.
A traitor to the land and he betrays land and people and goes into the border region of the Saxons and gets from there the high helmet and the red shield and the armed knight and he goes into the land of the Frisians and kills men and burns strongholds, then he should be taken northwards to the sea and be thrown in the sea.
“To be taken north and thrown in the sea” meant not going for a refreshing swim at the North Sea beach, or a stroll over the mud flats of the Wadden Sea. No, it meant the person was being drowned. It could be even worse. If you had violated a religious sanctuary, you were castrated and your ears were split as well before being tied up to a pole during ebb. Then wait for the flood to come. In modern law the ‘traitor’ or foreign fighter is no longer stripped from his life, testicles, ears, et cetera, but stripped from his nationality. So, from something tangible to something fictional, some might argue.
Be that as it may, the keen reader may have deduced already that the fact returning foreign fighters had been killing, plundering and raping outside Frisia, was totally irrelevant for retaking their possessions or for some kind of corrective punishment. Neither was it seen as a traitorous act. Indeed, it underlines no international criminal law was applicable (yet). As it happens, former West Frisia is proud to have the Capital of International Law on its territory today, with all the international courts that go with it, namely The Hague.
Since Frisia was a flourishing feud society another option might also have been applicable, namely that the homecoming foreign fighter who had been killing and alike among his own people in Frisia and without being forced to do so by a master, could compensate the victim’s family and his or her relatives by paying a ‘fine’ together with a possible fine to restore the broken peace. After having paid these fines or weregild (see below) you could take possession of your property again.
To give you an idea of the fines that had to paid in these cases, the following:
If you killed a person you had to pay a weregild, or wergeld, meaning ‘man price’. A weregild for a killing a free man, or freeman, amounted 1,664 grams of fine silver. This amount of silver was more or less stable irrespective all different conversions with coins like dinari, solidi, sceattas, marks, pounds, et cetera in the legal texts through time. Yes, it stayed stable throughout the whole Middle Ages. Research has been done into the still-existing fines of the Kamba tribe in the Mashariki region in Kenya. There, a weregild amounts fourteen cows and one bull for killing a man. For a woman it is seven cows and one bull. And, to answer your pressing question: within Frisia (and East Anglia) the weregild for a woman was the same as that for a man, of the same social status, of course. In other Germanic tribes, however, the weregild for a woman was mostly higher. Sometimes three times as much, especially if she had reached the age of fertility. If you want to understand the logic of these differences better, read our blog post Women of Frisia: free and unbound? When you convert the weregeld of 1,664 grams into a current money of payment (date of this post) it would be for example 1,193 US dollar you had to pay to the heirs.
One of the Viking hoards found at the former island of Wieringen in the Netherlands contains exactly 1.7 kilograms of silver (see image above). The silver pieces are complete ornaments and unfragmented heavy silver ignots (Besteman 2009). It is the so-called Westerklief I silver hoard and dated ca. 850. Was it a weregild, or is it just coincidence? And if it was a weregild, what was a northeska wigandum (‘northern fighter’ in Old-Frisian speech, denoting a Viking) doing with a weregild in Frisia territory? We do not know. Create your own story! If interested in the function of weregeld read our blog post You killed a Man? That’ll be 1 weregeld, please.
Note 1 – The raids of the Viking are the thing often focused at, when we talk about raiding in northern Europe. In fact, the wider North Sea had a long-standing tradition of piracy. The first five centuries of the common era, piracy was wide-spread and extended from the southern coast of the North Sea to Britannia, Gaul and all the way to the Mediterranean. Read our blog post It all began with piracy.
Note 2 – Quite a number of Vikings have found Walhalla on Frisia territory in the ninth century. Do a body count reading our blog post Frisia, a Viking graveyard.
Note 3 – Besides the Westerklief I silver hoard dated ca. 850, also the Westerklief II silver hoard is found at the same plot of land at Wieringen. This smaller (0,5 kilograms of silver) hoard is dated ca. 876 and contains mainly small hacksilver. Its coins are Arabic (this contrary to the Westerklief I hoard that contains nearly no Arabic coins), and originate mostly from present-day southern Iraq. Like the Westerklief I hoard, also the Westerklief II is of Viking of origin (Besteman 2009).
Suggestions for further reading:
- Besteman, J., A second Viking hoard from Wieringen: Westerklief II (2009)
- Bremmer, R.H., Hir is eskriven. Lezen en schrijven in de Friese landen rond 1300 (2004)
- Bos-van der Heide, H.S.E., Het Rudolfsboek (1937)
- Coupland, S., Recent Finds of Imitation Gold Solidi in the Netherlands, The Numismatic Chronicle 176 (2016)
- Engelkes, G.G., Der schwarze Rolf (1936)
- Finlay, A. cs (ed), Saga-Book Vol. XL (2016)
- Heide, E., Viking – ‘Rower shifting?’ An etymological contribution (2005)
- Henstra, D.J., The evolution of the money standard in medieval Frisia. A treatise on the history of the systems of money of account in the former Frisia (c. 600 – c.1500) (1999)
- IJssennagger, N.L., Between the Frankish and the Vikings: Frisia and the Frisians in the Viking Age (2017)
- IJssennagger, N.L., Central because Liminal. Frisia in a Viking Age North Sea World (2017)
- Jacobs, T.J.M., Friese vosten (2020)
- Klæsøe, I.S. (ed), Viking Trade and Settlement in Continental Western Europe (2010)
- Lewis, S.M., Rodulf and Ubba. In search of the Frisian-Danish Viking (2018)
- Margaryan, A, et al, Population genomics of the Viking world (2020)
- Meertens Instituut, Corpus of First Names in The Netherlands, Nederlandse voornamen (website)
- Nieuwenhuijsen, K., Lex Frisionum. Inleiding (2010)
- Nijdam, H., Klinkende munten en klinkende botsplinters in Oudfriese rechtsteksten: continuïteit, discontinuïteit, intertekstualiteit (2009)
- Nijdam, H., Lichaam, eer en recht in middeleeuws Friesland. Een studie naar de Oudfriese boeteregisters (2008)
- Siems, H., Studien zur Lex Frisionum (1980)
- Stoter, M. & Spiekhout, D. (eds), Wij Vikingen. Friezen en Vikingen in het kustgebied van de Lage Landen (2019)
- Tuuk, van der L., De Friezen. De vroegste geschiedenis van het Nederlands kustgebied (2013)
- Tuuk, van der L. & Mijderwijk, L., De Middeleeuwers. Mannen en vrouwen uit de Lage Landen, 450-900 (2020)
- Vries, O., Asega, is het dingtijd? De hoogtepunten van de Oudfriese tekstoverlevering (2007)
- Vries, O., De taal van recht en vrijheid. Studies over middeleeuws Friesland (2012)
- Vries, O., De wylde Wytsing (2019)
- Willemsen, A., Gouden Middeleeuwen. Nederland in de Merovingische wereld, 400 – 700 na Chr. (2014)