Wrensch, Dana L., author
Kendall/Hunt, 1992
Buku Teks
Lewis, Ricki, author
McGraw-HIll, 1999
Buku Teks
Gutteridge, Anne C.
Cambridge University Press, 1983
Buku Referensi
Mader, Sylvia S., author
Iowa Wm. C. Brown, 1995
Buku Teks
Mader, Sylvia S., author
Wm. C. Brown Publisher, 1993
Buku Teks