English Language Services; editor, Charles J. Hirsch, James A. Curtin
Collier/Macmillan, 1970
Buku Teks
Rangkuti-Hasibuan, Sofia
Gramedia, 1986
Buku Teks
Harrison, G.B.
Penguin Books , 1953
Buku Teks
McGraw-Hill, 1964
Buku Teks
Honey, William Bowyer, 1889-
George Routledge & Sons, 1947
Buku Teks