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
The latter part of June, 1941, one live and two dead pigs, weighing about thirty pounds each, were presented at the Diagnostic Laboratory, University of Minnesota, for the diagnosis of a herd problem.
Hoyt, H. H.
""Clay Pigeon" Poisoning in Swine,"
Iowa State University Veterinarian: Vol. 4
, Article 14.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol4/iss1/14