Sackheim, George I.
Macmillan, 1973
Buku Teks
Oxtoby, David W.
Thomson, Brooks/Cole, 2003
Buku Teks
Seager, Spencer L.
Scott, Forestman and Company, 1973
Buku Teks
Brown, Theodore L.
Prentice-Hall, 1991
Buku Teks
Helmprecht, H.L.
McGraw-Hill, 1977
Buku Teks