De Blij, Harm J., author
John Wiley & Sons, 1996
Buku Referensi
Petersen, James F., author
Brooks/Cole Cengage Learning, 2012
Buku Teks
Muller, Robert A., author
Random House, 1978
Buku Teks
Craghan, Michael, author
John Wiley & Sons, 2003
Buku Teks
Strahler, Arthur N., author
John Wiley & Sons, 1983
Buku Teks