Practically since the ASJU (International Journal of Basque Linguistics and Philology) was first published, this collection has also published first-rate research monographs as appendices. As well as Nicolao Landucci's edition of the Dictionarium Linguae Cantabricae, Mitxelena's historical phonetics and many other works, especially after 1990.
These books address different aspects of synchronic linguistics, dialectology, the history of Euskera, as well as its literature and philology (from textual criticism to critical edition).
They occasionally contain writings from congresses and meetings. Also, understanding the word "vascología" (Basque-ology) in the broadest sense of the word, as did the creator and director of the ASJU Koldo Mitxelena, they include other books that, without being directly related to Euskera, may be important for "vascología", as well as for all other fields of philology and linguistics.
Dozens of titles have already featured in these appendices to the ASJU, including the Complete Works of Koldo Mitxelena, published in 2011-2012, previous collections of the works of some important "vascólogos" (people skilled in Basque studies) (Rudolf P. G. de Rijk and George Rebuschir, among others), and tributes made to some of them: the tribute to Mitxelena in 1991, followed by tributes to Rijk, Larry Traski, Patxi Goenaga and Beñat Oihartzabal.
The aforementioned books and those soon to be published make the ASJU supplements, as well as the journal itself, essential reading for researchers and students who are working in the field of the Basque language. Overall, it may contain interesting material for experts in other fields of philology and linguistics and also for all Basque speakers.