G & C Merriam Co., 1947
Buku Referensi
Lexicon Publications , 2004
Buku Referensi
Scott-Kilvert, Ian, author
Longmans, Green, 1970
Buku Teks
G & C Merriam Co., 1951
Buku Referensi
Neufeldt, Victoria, author
Prentice Hall ; Modern English Press, 1993
Buku Referensi