(EN) Müller, André, Viveka Velupillai, Søren Wichmann, Cecil H. Brown, Eric W. Holman, Sebastian Sauppe, Pamela Brown, Harald Hammarström, Oleg Belyaev, Johann-Mattis List, Dik Bakker, Dmitri Egorov, Matthias Urban, Robert Mailhammer, Matthew S. Dryer, Evgenia Korovina, David Beck, Helen Geyer, Pattie Epps, Anthony Grant, and Pilar Valenzuela. 2013. ASJP World Language Trees of Lexical Similarity: versione 4 (ottobre 2013).
rinet.ru
starling.rinet.ru
(EN) Nikolayev, S., and S. Starostin. 1994 North Caucasian Etymological Dictionary. Moscow: Asterisk Press. Disponibile online.
