(en) Giacomo Giammatteo, How to Capitalize Anything, Inferno Publishing Company, (lire en ligne), p. 181.
(en) Rural Heritage, Freiberg-Frederick Press, (lire en ligne), p. 56.
(en) Valerie Porter, Mason's World Dictionary of Livestock Breeds, Types and Varieties, 6th Edition, CABI, (ISBN978-1-78924-153-2, lire en ligne), p. 221.