Bell, Gerard D., author
Prentice-Hall, 1967
Buku Teks
French, Wendell L., author
Harper & Row, 1985.
Buku Teks
Hasenfeld, Yeheskel, author
Sage, 2016
Buku Teks
Dunkerly, David
Routledge, 1972
Buku Teks
Peter, Chris Maina
Greendwood Press, 1990
Buku Teks