Seager, Spencer L.
Brooks/Cole, 2008
Buku Teks SO
Seager, Spencer L.
St. Paul West Publishing, 1994
Buku Teks SO
Oxtoby, David W.
Thomson, Brooks/Cole, 2003
Buku Teks SO
Brown, Theodore L.
Prentice-Hall, 1977
Buku Teks SO
Brown, Theodore L.
Prentice-Hall, 1991
Buku Teks SO