1. Hock, Hans Henrich. 1991. Principles of historical linguistics, 2nd edition. Berlin and New York: Mouton de Gruyter
2. Celtic influence in English
3. Zur Entstellung des Englischen Participium Praesentis auf -ing;Dal;Norsk tidskrift for sprogvidenskap,1952
4. Notes on continuous tenses in English;Braaten;Norsk tidskrift for sprogvidenskap,1967
5. Kytö, Merja. 1991. Manual to the diachronic part of the Helsinki Corpus of English Texts. Helsinki: Department of English, University of Helsinki