Literature
- Parker, S. B. 1982. Synopsis and classification of living organism. McGraw-Hill, New York.
- Romer, A. S. and Parsons, T. S. 1977. The vertebrate body , 5th ed. Saunders, Philadelphia.
- Vaughan, T. A. 1978. Mammalogy, 2d ed., W. B. Saunders, Philadelphia.