Não informado. (2001). Pig improvement services. Meat and Livestock Commission.
Chicago-referens (17:e uppl.)Não informado. Pig Improvement Services. Bletchley, Inglaterra: Meat and Livestock Commission, 2001.
MLA-referens (8:e uppl.)Não informado. Pig Improvement Services. Meat and Livestock Commission, 2001.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.