edited by Carl K. Seyfert
Van Nostrand Reinhold, 1987
Buku Referensi
Sutherland, Lin, author
University of New South Wales Press, 1995
Buku Referensi
Chester, Roy, author
American Management Association, 2008
eBooks
Ballard, Robert D., author
National Geographic Society, 1983
Buku Referensi
Bowler, Sue, author
Erlangga, 2003
Buku Teks