Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Control of diseases in domestic animals is attempted for two main reasons: 1. To reduce reservoirs of disease transmissible to man, and 2. to produce livestock more economically.
Spear, Maynard L.
"Specific Pathogen Free Swine,"
Iowa State University Veterinarian: Vol. 22
, Article 2.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol22/iss3/2