1. Scientific Veterinary Committee: The Welfare of Intensively Kept Pigs. Report of the Scientific Veterinary Committee. 1997, European Union, Brussels
2. Barnett JL, Hemsworth PH, Cronin GM, Jongman EC, Hutson GD: A review of the welfare issues for sows and piglets in relation to housing. Austral J Agric Res. 2001, 52: 1-28. 10.1071/AR00057.
3. Harrison R: Animal Machines. 1964, Vincent Stuart Ltd, London
4. Singer P: Animal Liberation. (1st edition 1975). 1990, Avon Books, New York, 2
5. Brambell FWR: Report of the Technical Committee to Enquire into the Welfare of Animals kept under Intensive Livestock Husbandry Systems. 1965, Her Majesty's Stationery Office, London