Fronment, Gilbert F., author
John Wiley & Sons, 1979
Buku Teks
Houston, Paul L, author
McGraw-Hill , 2001
Buku Teks
Smith, J. M., author
McGraw-Hill, 1981
Buku Teks
Holland, Charles D., author
Prentice-Hall, 1989
Buku Teks
Dadzie, Stella
National Institute of Adult Continuing Education, 1993
Buku Teks