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 Jan. 26, 1957, a 3 year old Guernsey cow was brought to Stange Memorial Clinic because of dystocia. Dr. D. E. Gubser of Earlham, Iowa, had diagnosed a two-headed calf in anterior presentation causing the dystocia and recommended sending the cow to the clinic for cesarean section.
"Two-Headed Calf Causes Dystocia,"
Iowa State University Veterinarian: Vol. 19
, Article 9.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol19/iss2/9