He took the Doctor of Philosophy degree in 1988 with the thesis Holt og Holtar.
Om utviklingen av det indoeuropeiske kollektivum i norrønt på sammenlignende grunnlag.
[1] His fields of specialty are general comparative language history, general Indo-Germanic linguistics, all archaic Germanic languages (Old West Norse, Gothic, Old High German etc.
), and Germanic linguistics in general, including runes, morphology, and etymology.
[2] His most famous work is a new etymological dictionary (Våre Arveord "Our inherited words") for Norwegian, which is a collaboration with Fredrik Otto Lindeman, another linguist professor in the Indo-Germanic field.