^ Fortson, Benjamin W. (2004, 2010) Indo-European Language and Culture: An Introduction, Oxford: Blackwell
^ Beekes, Robert S. P. (2011) Comparative Indo-European Linguistics: An Introduction, revised and corrected by Michiel de Vaan, 2nd edition, Amsterdam, Philadelphia: John Benjamins Publishing Company, page 238
^ Martirosyan, Hrach (2010), “inn-sun”, in Etymological Dictionary of the Armenian Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 8), Leiden and Boston: Brill, page 302
^ Beekes, Robert S. P. (2010), “ἐνενήκοντα”, in Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), with the assistance of Lucien van Beek, Leiden, Boston: Brill, →ISBN, page 423
^ De Vaan, Michiel (2008), “-gintā”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, pages 262
^ De Vaan, Michiel (2008), “novem”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, pages 415
^ Adams, Douglas Q. (2013), “ñumka ~ ñuṅka”, in A Dictionary of Tocharian B: Revised and Greatly Enlarged (Leiden Studies in Indo-European; 10), Amsterdam, New York: Rodopi, →ISBN, page 287
