Fokkema, K.. 1937. ‘Frisian Studies’, in The Year's Work in Modern Language Studies, Volume 8: Survey Year 1937, The Year's Work in Modern Language Studies, 8 (MHRA), pp. 228–32, doi:10.2307/25833452
Fokkema, K.. 1937. ‘Frisian Studies’, in The Year's Work in Modern Language Studies, Volume 8: Survey Year 1937, The Year's Work in Modern Language Studies, 8 (MHRA), pp. 228–32, doi:10.2307/25833452