Não informado. (2001). Pig improvement services. Meat and Livestock Commission.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Pig Improvement Services. Bletchley, Inglaterra: Meat and Livestock Commission, 2001.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Pig Improvement Services. Meat and Livestock Commission, 2001.
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