Drago, Carl, author
Blackwell Publishing, 2007
Buku Referensi
Kemp, Marwin K., 1942-, author
Academic Press, c1979
Buku Teks
Helms, Michael E., author
Prentice-Hall, 1990
Buku Referensi
Ziegler, Kathleen, author
Rockport Publishers, 1994
Buku Referensi
Drago, Carl, author
Blackwell, 2014
Buku Teks