edited by Kreg Lindberg and Donald E. Hawkins
Ecotourism Society, 1993
Buku Teks
Stewart, Rosemary, author
Macmillan, 1993
Buku Teks
Sashkin, Marshall, 1944-, author
American Managemant Association, 1982
Buku Teks
Hofer Press, 1991
Buku Teks
APA Publications, [date of publication not identified]
Buku Referensi