Haugen, E., 1972, The ecology of language, Stanford University Press. (Dil, A.S. ed.). GI-03; GI-05; GI-19; PA-05 Gako-hitzak: Hizkuntza (ekologia)
Haugen, E., 1976, The Scandinavian languages: an introduction to their history, Londres: Faber & Faber. GI-03; PA-05 Gako-hitzak: Eskandinavia; Hizkuntza