Gray, Robert, author
Duffy and Snellgrove, 1996
Buku Teks
Wallach, Paul L., author
McGraw-Hill, 1979
Buku Teks
Callaghan, Barry
General Publishing Co. Limited, 1978
Buku Teks
Burns, Robert C.
New York, 1982
Buku Teks
Thomas, Marvin L.
New York: McGraw-Hill, 1978
Buku Teks