Garcia-Nunez, Jose
Kumarian Press, 1992
Buku Referensi
Talley, Dorsey J.
ASQC Quality Press , 1988
Buku Teks
Thompson, Leigh L.
Pearson/Prentice Hall, 2004
Buku Teks
Sashkin, Marshall, 1944-
American Managemant Association, 1982
Buku Teks
edited by Kreg Lindberg and Donald E. Hawkins
Ecotourism Society, 1993
Buku Teks