^Trumper, John. "Some Celto‑Albanian isoglosses and their implications." Structuring Variation in Romance Linguistics and Beyond. In honour of Leonardo M. Savoia (2018).
↑4.04.1Wodtko, Dagmar S.; Irslinger, Britta; Schneider, Carolin (2008), “*bʰei̯dʰ-”, inNomina im indogermanischen Lexikon [Nouns in the Indo-European Lexicon] (in German), Heidelberg: Universitätsverlag Winter, page12