Otero, George G., author
University of Denver, 1981
Buku Teks
Zelinsky, Wilbur, author
Prentice-Hall, 1966
Buku Teks
Gulati, P., author
Tata McGraw-Hill, 1984
Buku Teks
Zelinsky, Wilbur
Prentice Hall International, 1970
Buku Teks
Russell, Sir E. John
George Allen and Unwin, 1961
Buku Teks