1. Aitken, R. J., Richardson, D. W. & Hulme, M. (1984). Immunological interference with the properties of the zona pellucida.In D. B. Crighton (Ed.), Immunologicalaspects of reproduction in mammals (pp. 305-325). London: Bunenvorths.
2. Al-Kawafi, A. A., Hopwood, M. L., Pineda, M. H. & Faulker, L. C. (1974). Immunization of dogs against human chorionic gonadotropin. American Journal of Veterinan; Research, 35. 261-264.
3. Observational Study of Behavior: Sampling Methods
4. Asa, C. S., Porton, I., Baker, A. M. & Plotka, E. D. (1996). Contraception as a management tool for controlling s~lrplusanimals. InD. C;Kleiman, M. E. Allen, K. V. Thompson, & S. Lumpkin (Eds.), Wild mammals in captrvi&: Principles and techniques (pp.451-467). Chicago: University of Chicago Press.
5. A U contraception advisory group recommendations. (1995). Silver Spr~ng.MD: American Zoo & Aquarium Association.