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
On February 3, 1943, a two-year-old Hereford bull was presented at the Stange Memorial Clinic with a history of only occasionally breeding cows. His breeding activities for the last few months had been quite sporadic; in some instances he would breed quite normally while at other times he would pay no attention to the cows. The owner believed that the bull had settled three cows as they had not come in heat since they were bred.
"Infection as a Possible Cause of Sterility,"
Iowa State University Veterinarian: Vol. 5
, Article 12.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol5/iss4/12