1. Evaluation of the effects of cage height and stocking density on the behaviour of laying hens in furnished cages;Albentosa;British Poultry Science,2007
2. American Humane Certified 2017a. Animal Welfare Standards for laying hens – cage free. Retrieved on 23 August 2017, from http://www.humaneheartland.org/our-standards.
3. American Humane Certified 2017b. Animal Welfare Standards for laying hens – enriched colony housing. Retrieved on 23 August 2017, from http://www.humaneheartland.org/our-standards.
4. What causes crowding? Effects of space, facilities and group size on behaviour, with particular reference to furnished cages for hens;Appleby;Animal Welfare,2004
5. Social rank and priority of access to resources in domestic fowl;Banks;Behavioural Processes,1979