Wooster, Chuck (2005). Living with Sheep: Everything You Need to Know to Raise Your Own Flock. Geoff Hansen (Photography). Guilford, Connecticut: The Lyons Press. ISBN 1-59228-531-7.
Craftwar, Cody (2007-01-25). "Life and Love Amongst The Sheep: A Biography". The New York Times. Truy cập 2007-12-07.
Padula, A.M. (2005). "The freemartin syndrome: an update". Animal Reproduction Science. 87 (1/2): 93–109. doi:10.1016/j.anireprosci.2004.09.008. PMID 15885443
Simmons, Paula; Carol Ekarius (2001). Storey's Guide to Raising Sheep. North Adams, MA: Storey Publishing LLC. ISBN 978-1-58017-262-2.
Smith M.S., Barbara; Mark Aseltine PhD; Gerald Kennedy DVM (1997). Beginning Shepherd's Manual, Second Edition. Ames, Iowa: Iowa State University Press. ISBN 0-8138-2799-X.
Weaver, Sue (2005). Sheep: small-scale sheep keeping for pleasure and profit. 3 Burroughs Irvine, CA 92618: Hobby Farm Press, an imprint of BowTie Press, a division of BowTie Inc. ISBN 1-931993-49-1.
Cottle, D.J. (1991). Australian Sheep and Wool Handbook. Inkata Press, Melbourne. ISBN 0-909605-60-2.
