Goodall, Brian
Penguin Books, 1987
Buku Referensi
Moore, W. G.
Penguin Books, 1974
Buku Referensi
Moore, W.G.
London : Penguin Books, 1984,
Buku Referensi
Petersen, James F.
Brooks/Cole Cengage Learning, 2012
Buku Teks
Strahler, Arthur N.
John Wiley & Sons, 1975
Buku Teks