Beaumont, Henry
Longmans, Green and Co., 1945
Buku Teks
Ghiselli, Edwin E., author
McGraw-Hill, 1955
Buku Teks
edited by Edwin A. Fleishman
Dorsey Press, 1967
Buku Teks
Lefton, Lester A.
Allyn and bacon , 1997
Buku Teks
Wortman, Camille B., author
McGraw-Hill, 1992
Buku Teks