^ Derksen, Rick (2015) “troba”, in Etymological Dictionary of the Baltic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 13), Leiden, Boston: Brill, →ISBN, page 472
^ De Vaan, Michiel (2008) “trabs, -is”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 626