Burton, Steven J.
West Publishing Co., 1995
Buku Teks
Colander, David C., author
McGraw-Hill , 1998
Buku Teks
Colander, David C., author
McGraw-Hill, 2004
Buku Teks
Raup, David M.
W.H. Freeman and Co., 1978
Buku Teks
Dallin, David J.
Yale University Press, 1949
Buku Teks