1. American Pet Products Manufacturers Association. (1996). APPMA nationalpet owners survey.Greenwich. CT: Author.
2. Dean, A. G., Dean, J. A., Coulombier, D., Brendel, K. A , Smith, D. C., Burton, A. t i . , Dicker, R. C., Sullivan, K., Fagan, R. F. & Amer,T. 0. (1994).Epi Info (Version 6) [Computer software]. Atlanta, GA: Centers for Disease Control and Prevention.
3. Dixon, W. J. (1992). BMDP statistical sofrware (Version 7) [Computer software].Bognor Regis, England: Wiley.
4. Successful and Unsuccessful PET Adoptions