Davenport, S.J.
Washington, DC: United States Department of the Interior, 1954
Buku Teks
Nangoy, Eddy
Fakultas Kesehatan Masyarakat Universitas Indonesia, 1993
UI - Tesis Membership
Paul L. Magill, Francis R. Holden, Charles Ackley, editor; Frederick G. Sawyer, editorial consultant
McGraw-Hill, 1956
Buku Referensi
edited by Bhola R. Gurjar, Luisa T. Molina, Chandra S. P. Ojha ; foreword by Mario J. Molina
CRC Pres, 2010
Buku Teks
Cooper, C. David
Waveland Press, 1986
Buku Teks SO