Pfeifer, Wolfgang; et al., eds. (1993). "Tag". Etymologisches Wörterbuch des Deutsche [Etymological Dictionary of German] (in German) (print ed.).
digitalized as
Pfeifer, Wolfgang (ed.). "Tag". Digitalen Wörterbuch der deutschen Sprache [Deigital Dictionary of the German Language] (in German) (online ed.). Berlin-Brandenburg Science Academy. Retrieved 16 September 2023.