Glover, John Desmond, author
Richard D. Irwin, 1957
Buku Teks
Cascio, Wayne F., author
Prentice-Hall, 1998
Buku Teks
Tregold, R.F., author
International University Press, 1950
Buku Teks
Harper & Row, Pub., 1979
Buku Teks
Gazda, George M., author
Allyn and Bacon , 1975
Buku Teks