Elkan, Walter
The English Language Book Society ; Penguin Books, 1973
Buku Teks
Norton, George W., author
McGraw-Hill, 1993
Buku Teks
Cairncross, Alec, author
Butterworth, 1960
Buku Teks
Johnson, Alvin S., author
Hearh & Co., 1911
Buku Teks
Morgan, Theodore, author
Prentice-Hall, 1950
Buku Teks