Bradgate, Robert, author
Butterworth, 1991
Buku Teks
Goode, Roy, author
Penguin Books, 2004
Buku Teks
Savage, Nigel
Butterworth, 1991
Buku Teks
Hewiit, Charles M., author
Houghton Mifflin, 1962
Buku Teks
Simpson, Laurence P., author
Alexander Hamilton Institute, 1961
Buku Teks