Cooper, C. David, author
Waveland Press, 1986
Buku Teks
Davenport, S.J.
Washington, DC: United States Department of the Interior, 1954
Buku Teks
Paul L. Magill, Francis R. Holden, Charles Ackley, editor; Frederick G. Sawyer, editorial consultant
McGraw-Hill, 1956
Buku Referensi
Heihnson, Robert Jennings, author
Prentice-Hall, 1999
Buku Teks
edited by Bhola R. Gurjar, Luisa T. Molina, Chandra S. P. Ojha ; foreword by Mario J. Molina
CRC Pres, 2010
Buku Teks