Colm, Gerhard, author
National Planning Association , 1961
Buku Teks
Hang, Chuon Naron, author
Institute of South East Asia Studies, 2012
eBooks
Downs, Anthony, author
Markham Publishing, 1970
Buku Teks
edited by Steven W. Hays, Richard C. Kearney
Prentice-Hall, 1990
Buku Teks
Peters, Gary L., author
Kendall/Hunt, 1983
Buku Teks