Mahood, H. R.
Scribner, 1967
Buku Teks
Smucker, Bob
Jossey - Bass Publishers, 1991
Buku Teks
edited by Barry B. Baker
The Haworth Press, 1993
Buku Teks
Marsh, Donald Bailey
Jaques Cattel Press , 1945
Buku Teks
Hall, Milton
Civil Service Assembly, 1948
Buku Teks