Marks, Trevor E., author
William Ernest, 1992
Buku Teks
Boston, 1989
Buku Teks
Whitfield, John, author
EPA Press, 1995
Buku Referensi
Jenkins, Brian D. (Brian David), author
Blackwell Scientific Publications, 1991
Buku Teks
edited by Charles A. Harper
McGraw-Hill, 1972
Buku Referensi