^ Wodtko, Dagmar S., Irslinger, Britta, Schneider, Carolin (2008) “*h₂ek̑-”, in Nomina im indogermanischen Lexikon [Nouns in the Indo-European Lexicon] (in German), Heidelberg: Universitätsverlag Winter, pages 287-300
^ De Vaan, Michiel (2008) “ocris”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 424