1. United States Department of Agriculture. Livestock Slaughter, various dates.
2. United States Department of Agriculture. Poultry Slaughter, various dates.
3. Anderson, J. R., & Gallup, G. G. (1999). Self-recognition in nonhuman primates: Past and future challenges. In M. Haug & R. E. Whalen (Eds.), Animal models of human emotion and cognition (pp. 175–194). Washington, DC: American Psychological Association.
4. Austic, R. E., & Neshem, M. C. (1990). Poultry production (13th ed.). Philadelphia, PA: Lea & Febiger.
5. Bateson, P. (1991). Assessment of pain in animals. Animal Behavior, 42, 827–839.