András Róna-Tas, An introduction to Turkology, Universitas Szegediensis de Attila József Nominata, 1991, p. 29.
Anatoly Michailovich Khazanov, Nomads and the Outside World, Univ of Wisconsin Press, 1984, ISBN 978-0-299-14284-1, p. 256.
Elena Vladimirovna Boĭkova, R. B. Rybakov, Kinship in the Altaic World: Proceedings of the 48th Permanent International Altaistic Conference, Moscow 10-15 July 2005, Otto Harrassowitz Verlag, 2006, ISBN 978-3-447-05416-4, p. 225.