Clark, John R., author
Lewis Publishers, 1996
Buku Referensi
Beatley, Timothy, author
University California Press, 2003
Buku Teks
John Wiley , 1972
Buku Teks
School for Resource and Environmental Studies Dalhousil University , 1988
Buku Teks
McGraw-Hill, 2000
Buku Referensi