Levesque, Joseph D., author
Prentice-Hall, 1996
Buku Referensi
Goss, Sue, author
HMSO, Department of the Environment, 1994
Buku Referensi
Napitupulu, Daniel, author
2004
Artikel Jurnal
Coyne, John, author
Macmillan, 1987
Buku Teks
Kuong, Javier F., author
Prentice-Hall, 1987
Buku Teks