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
This comprises a group of diseases usually most prevalent during the fall and winter months. Many times diagnosis is difficult due to the similarity of symptoms of many of the disorders. In many instances this group of diseases is predisposed by faulty management or by nutritional deficiencies, particularly Vitamin A.
Lee, C. D.
Iowa State University Veterinarian: Vol. 4
, Article 6.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol4/iss1/6