Krug, Ronald S.
Springer-Verlag, 1992
Buku Teks
Gravetter, Frederick J.
Thomson Learning, 2000
Buku Teks
Gravetter, Frederick J.
Wadsworth/Thomson Learning, 2004
Buku Teks
Kaplan, Robert M.
Allyn and Bacon , 1987
Buku Teks
Siegel, Sidney
McGraw-Hill, 1956
Buku Teks