Schuster, Frederick E.
Reston, 1985
Buku Teks
Steiner, George Albert, 1912-
Macmillan, 1977
Buku Teks
edited by Frank W. Moore
HRAF Press, 1961
Buku Teks SO
Lewicki, Roy J.
McGraw-Hill, 2000
Buku Teks SO
Roy J. Lewicki, Saunders David M., Minton John W., Barry Bruce
McGraw-HIll, 2003
Buku Teks