Howell, David C., author
Thomson Higher Education, 2004
Buku Teks
edited by Roger Penn, Damon Berridge
Sage, 2013
Buku Teks
Knoke, David, author
Thomson, 2002
Buku Teks
Hopkins, Kenneth D., author
Allyn And Bacon, 1987
Buku Teks
Connolly, T.G.
Hafner , 1953
Buku Teks