^Mayrhofer, Manfred (1992) “ká-1”, inEtymologisches Wörterbuch des Altindoarischen [Etymological Dictionary of Old Indo-Aryan][1] (in German), volume I, Heidelberg: Carl Winter Universitätsverlag, page284
^Martínez García, Javier,de Vaan, Michiel (2014)Introduction to Avestan (Brill Introductions to Indo-European Languages; 1)[2], Brill,→ISBN, page15