^Matasović, Ranko (2009), “*kʷal-na-”, li ser Etymological Dictionary of Proto-Celtic (Leiden Indo-European Etymological Dictionary Series; 9), Leiden: Brill, →ISBN, rûpel 174
^Robert S. P. Beekes (2010), Etymological Dictionary of Greek (Leiden Indo-European Etymological Dictionary Series; 10), with the assistance of Lucien van Beek, Leiden, Boston: Brill, →ISBN, rûpel 1462
