1. Pimental D, Loch L, Zuninga R and Morrison D, Environmental and Economic Costs Associated with Non-indigenous Species in the United States. [Online]. Available: http://www.news.cornell.edu/releases/Jan99/species_costs.html [13 July 2009].
2. The welfare of free-living wild animals: methods of assessment;Kirkwood;Anim Welfare,1994
3. The role of ethics in the management of New Zealand's wild mammals;Eggleston;N Z J Zool,2003
4. Ethical issues associated with possum research and control in New Zealand;Morris;J Agric Environ Ethics,2003
5. Physiology and Behaviour of Animal Suffering