Hewitt, Paul G., author
Pearson - Addison Wesley, 2008
Buku Teks
Trewartha, Glenn T., author
McGraw-Hill, 1967
Buku Teks
Haggett, Peter, author
Prentice-Hall, 2001
Buku Teks
Boyce, Ronald Reed, author
John Wiley & Sons, 1982
Buku Teks
Routledge, 1991
Buku Teks