::I've found Östen Dahl, 2001, The Circum-Baltic Languages: Typology and Contact, vol. 1. I don't have enough access to always be able distinguish when "Curonian" is referring to Old Curonian ws. modern Curonian dialects of Lithuanian, but at least one author in that collection says that it is now generally accepted that it was an Eastern Baltic language intermediate between Lithuanian and Latvian (though also mentioning some would say between E & W Baltic), and discusses the morphological evidence (most of which I can't see). —