1. Allen, C., Bekoff, M., 1995. Function, natural design, and animal behavior: philosophical and ethological considerations. In: Thompson, N.S. (Ed.), Perspectives in Ethology, Vol. 11 (Behavioral Design). Plenum, New York, USA, pp. 1–46.
2. Baenninger, R., 1990. Consciousness and comparative psychology. In: Johnson, M.G., Henley, T.B. (Eds.), Reflections on the Principles of Psychology: William James After a Century. Erlbaum, Hillsdale, USA, pp. 249–269.
3. Beauchamp, T.L., Childress, J.F., 1994. Principles of Biomedical Ethics, 4th edn. Oxford Univ. Press, New York, USA.
4. Cognitive ethology and the treatment of non-human animals: how matters of mind inform matters of welfare;Bekoff;Anim. Welfare,1994
5. Blatz, C.V., 1991. Why (most) humans are more important than other animals. In: Blatz, C.V. (Ed.), Ethics and Agriculture. University of Idaho Press, Moscow, USA, pp. 478–487.