Chapin, Albert F., author
McGraw-Hill, 1960
Buku Teks
Wells, William D., author
Prentice-Hall, 1998
Buku Teks
by James J. Nora [and others]
[publisher not identified], [date of publication not identified]
Buku Teks
Wells, William D., author
Prentice-Hall, 2000
Buku Teks
Hammersly, Martyn, author
Routledge, l995
Buku Teks