Bregman, Allyn
John Wiley & Sons, 1990
Buku Teks
Norstog, Knut
Northern Illinois University, 1969
Buku Teks
Choinski, John S.
Wm.C. Brown Pub., 1992
Buku Teks
Gardner, Eldon J.
Burgess, 1975
Buku Teks
Vodopich, Darrell S.
McGraw-Hill , 2005
Buku Teks