edited by Dwight Waldo
McGraw-Hill, 1953
Buku Teks
Sharkansky, Ira, author
Rand McNally College Publishing Company, 1975
Buku Teks
Artikel Jurnal
Terry, Charles W., author
USOM, 1959
Buku Teks
edited by Martin Kriesberg
Brooking Institute, 1966
Buku Teks