Spencer, R. A.
Edward Arnold & Co, [date of publication not identified]
Buku Teks
Skaife, Linda
National Textbook Company, 1994
Buku Teks
Rybak, Stephanie
Macmillan and Co., 1985
Buku Teks
Whitmarsh, W. F. H.
Longmans, Green and Co., 1960
Buku Teks
Carpenter, Catrine
Gramedia Widiasarana Indonesia, 2000
Buku Teks