Oxtoby, David W., author
Thomson, Brooks/Cole, 2003
Buku Teks
Seager, Spencer L., author
Scott, Forestman and Company, 1973
Buku Teks
Helmprecht, H.L., author
McGraw-Hill, 1977
Buku Teks
Sackheim, George I., author
Macmillan, 1977
Buku Teks
Moore, John W., author
Thomson Brooks/Cole, 2005
Buku Teks