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
A patient, a seven year old purebred Angus cow, was presented at Stange Memorial Clinic on Jan. 8, 1941. She had begun labor the previous night after having completed a gestation period of supposedly normal length.
Kyner, R. E.
Iowa State University Veterinarian: Vol. 3
, Article 12.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol3/iss3/12