1. C S Bailey, J P Morgan, and S J Ettinger (1983 )-Textbook of Veterinary Internal Medicine. Diseases of the Dog and Cat , Saunders, W B, Philadelphia, p564 .
2. D R Cordy, and J E Moulton (1977 )-Tumours in Domestic Animals , 2nd edn , Univ of California Press, Berkleyp442 .
3. R. Fankhauser, H. Luginbuhl, and J J McGrath (1974 )-International Histological Classification of Tumours of Domestic Animals , Bull, WHO, Geneva, p56 , 56 .
4. B F Hoerlein (1978 )-Canine Neurology-Diagnosis and Treatment , Vol 1 , 3rd edn , Academic Press, New York, p495 .