Burton R. Clark, Guy R. Neave, editors-in-chief
Pergamon Press, 1992
Buku Referensi
Regan, William
Harper & Row, Publishers, 1970
Buku Teks
Bestor, Arthur
Knopf, 1956
Buku Teks
Johns, Roe L.,
Prentice-Hall, 1975
Buku Teks
Apps, Jerold W., author
Jossey-Bass , 1985
Buku Teks