↑Fortson, Benjamin W. (2004, 2010) Indo-European Language and Culture: An Introduction [印欧语系与文化:绪论], 牛津: Blackwell
↑Beekes, Robert S. P. (2011) Comparative Indo-European Linguistics: An Introduction [比较印欧语言学:导论], revised and corrected by Michiel de Vaan, 2nd版, Amsterdam, Philadelphia: John Benjamins Publishing Company, 页238