Gray, Peter, author
Worth Publishers, 1999
Buku Teks
Ciccarelli, Saundra K., author
Pearson - Prentice Hall, 2006
Buku Teks
Lefton, Lester A.
Allyn and bacon , 1997
Buku Teks
Munn, Norman L., author
Houghton-Mifflin, 1961
Buku Teks
Myers, David G., author
Worth Publisher, 1986
Buku Teks