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3. Welfare assessment and relevant ethical decisions: key concepts;BROOM;ARBS Annual Review of Biomedical Sciences,2008
4. DEFRA 2012 https://www.gov.uk/government/publications/zoos-expert-committeehandbook
5. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1999:094:0024:0026:EN:PDF