Handbuch des Friesischen =Horst Haider Munske, Nils Arhammar, Volkert F. Faltings, Jarich F. Hoekstra · First published 2001Open the Tome
Fourth International Conference on Minority LanguagesInternational Conference on Minority Languages (4th 1989 Leeuwarden, Netherlands), Durk Gorter, Jarich F. Hoekstra, Lammert G. Jansma · First published 1990Open the Tome
