Bartholomew, Paul C., author
W.M.C. Brown, 1951
Buku Teks
Wilson, James Q., author
D.C. Heath, 1995
Buku Teks
Wilson, James Q., author
D.C. Helath and Co., 1986
Buku Teks
edited by Stephen K. Bailey
United States Information Agency, 1973
Buku Teks
Schroeder, Richard C., author
International Communicational Agency, [date of publication not identified]
Buku Teks