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2. Animal Industry Act PA 466. § 46 (Amended 2009) 1988 Michigan
3. The European Union ban on conventional cages for laying hens: History and prospects;Appleby;J. Appl. Anim. Welf. Sci.,2003
4. What causes crowding? Effects of space, facilities and group size on behaviour, with particular reference to furnished cages for hens;Appleby;Anim. Welf.,2004
5. UEP uses scientific approach in its establishment of welfare guidelines;Bell;Feedstuffs,2004