Coombs, William E.
F.W. Dodge Co. , 1958
Buku Teks
Barrat, David
Routledge, 1994
Buku Teks SO
Calhoun, Richard P.
McGraw-Hill, 1958
Buku Teks
edited by Arthur A. Thompson, William E. Fulmer, A.J. Strickland
Irwin, 1992
Buku Teks
Henthon, William E.
Free Press, 1971
Buku Teks SO