Shaffer, Rick, author
Lowell House, 1999
Buku Referensi
Peters, Pamela, author
Wm.C. Brown Pub., 1993
Buku Referensi
Douglas-Young, John, author
Parker Publishing Company, 1978
Buku Referensi
Church, James C., author
McGraw-Hill, 1979
Buku Referensi
Levine, Morris E.
Prentice-Hall, 1982
Buku Teks