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
Leukemia in our domestic animals is not a rare occurrence, although some practitioners have never encountered a single case. Late in August, 1941, five clinical cases of leukemia were encountered by the Iowa State College ambulatory clinic, all in the same herd and within a five month period. The herd consisted of twenty-three females and two males of the milking shorthorn breed.
Held, H. E.
"Lymphatic Leukemia in Bovine,"
Iowa State University Veterinarian: Vol. 4
, Article 11.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol4/iss1/11