edited by Kathleen E. Hug
Office of International Infrmation Programs US Department of State, [Date of publication not identified]
Buku Teks
Baker, Ross K., author
Free Press, 1980
Buku Teks
Martin, Dick, author
American Management Association, 2007
eBooks
Sorokin, Pitirim A.
E. P. Dutton and Company, Inc., 1944
Buku Teks
Downs, Frederick
W.W. Norton & Company, 1991
Buku Teks