Askeland, Jan
Office of Cultural Relations, 1954
Buku Teks
Haugen, Einar
Stanford University Press, 1972
Buku Teks
Valette, Rebecca M., author
Harcourt, Brace & World, 1967
Buku Teks
Bloomfield, Leonard, author
Holt, Rinehart and Winston, 1961
Buku Teks
Whatmough, Joshua
The New American Library, 1956
Buku Teks