Tidwell, Gary L
John Wiley Sons Inc, 1993
Buku Teks
Guymon, Gary L.
Prentice-Hall, 1994
Buku Teks
Fuller, Lon L., author
Penguin Books, 1971
Buku Teks
Whitehouse, Gary E.
Chart, Diagrs , 1976
Buku Teks
Albrecht, Gary L.
Connecticut JAI Press, 1994
Buku Teks