Since 1998, Zuazo's work on the Basque dialects has drawn a new classification and a new map of these dialects—this has been a revolution in a field where few changes were made since Louis Lucien Bonaparte's works (1863).[2]
According to Zuazo, the Basque dialects (together with other language innovations) originated in urban areas:
The source of the Eastern dialect is not clear, Zuazo states that it may have happened in Bearn or in Huesca
Zuazo has observed that all dialects had a similar influence of Latin and therefore he thinks that all dialects originated after Roman times. This is aligned with Mitxelena's earlier thoughts on this subject.
Zuazo thinks that the Western dialect originated in Araba, based on the similarities between the dialects of Biscay, west of Navarre, the Deba valley and Goierri.
Bibliography
Non-fiction
Euskararen batasuna (The standardization of Basque language). Euskaltzaindia, 1988 - ISBN9788485479467
Euskararen sendabelarrak (Tips and solutions for some of the problems of Basque language). Alberdania, 2000 ISBN9788495589057
Euskara batua: ezina ekinez egina (The challenge of the standardization of Basque language). Elkar, 2005 ISBN9788490275191
Deba ibarreko euskara. Dialektologia eta tokiko batua (Basque language in the Deba Valley. Dialects and local standards). Badihardugu, 2006 ISBN9788461138135
Euskalkiak. Euskararen dialektoak (Description of the dialects of Basque language). Elkar, 2008 ISBN9788497836265
Sakanako euskara. Burundako hizkera (Basque language in the region of Burunda). Nafarroako Gobernua eta Euskaltzaindia, 2010 ISBN9788423532049
El euskera y sus dialectos (Basque language and its dialects). Alberdania, 2010 ISBN9788498682021
Uribe Kosta, Txorierri eta Mungialdeko euskara (Basque language in Uribe Kosta, Txorierri and Mungialde). UPV/EHU, 2016 (in collaboration with Urtzi Goitia) ISBN9788490824122
Euskalkiak (website): contains information about the standard Basque language and local standardsand dialects, combining text and media resources. Published in 2015 with the support of the University of the Basque Country. combining text and media resources. Published in 2015 with the support of the University of the Basque Country., . .
^Erdozia Mauleón, José Luis: "Sakanerak", Fontes linguae vasconum: Studia et documenta, ISSN 0046-435X, Year no. 37, no. 98, 2005, pages. 59-78. See page 60: "Bonaparte Printzearen sailkapenak indarrean iraun du duela urte gutxi arte euskal dialektologiaren baitan, Koldo Zuazo hizkuntzalariak Euskalkiak gaur (1998) lana aurkeztu zuen arte, hain zuzen ere."