Wolff, John U., compiler
Cornell University, 1972
Buku Referensi
Palmer, E.H.
Routledge & Kegan Paul, 1956
Buku Referensi
Wehr, Hans, 1909-1981
Spoken Language Services, 1976
Buku Referensi
Boyle, John Andrew
Luzac & Company, 1949
Buku Referensi
Macdonell, Arthur Anthony, 1854-1930
Oxford University Press, 1954
Buku Referensi