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
The feather, because of its relative simplicity, its availability, and its response to different physiological conditions that can be regulated quantitatively, is a valuable instrument for studies in various biological problems.
"Feather Morphology In Biological Research,"
Iowa State University Veterinarian: Vol. 10
, Article 4.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol10/iss1/4