↑ 1.01.1Sihler, Andrew L. (1995) New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN, page 396
^ Ringe, Donald (2006) From Proto-Indo-European to Proto-Germanic (A Linguistic History of English; 1)[1], Oxford: Oxford University Press, →ISBN
^ Beekes, Robert S. P. (2010) “τοῖος”, in Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), with the assistance of Lucien van Beek, Leiden, Boston: Brill, →ISBN, page 1491
^ Lubotsky, Alexander (2011) “yátra”, in The Indo-Aryan Inherited Lexicon (in progress) (Indo-European Etymological Dictionary Project), Leiden University