1. Ali, B. El Hag &Lees, G. E. (1979).Bulletin of Animal Health and Production in Africa,27, 1–6.
2. Alter, H. J., Holland, P. V. &Purcell, R. H. (1971).Journal of Laboratory and Clinical Medicine,77, 1000–1010.
3. Berlin, B. S. &Pirojboot, N. (1972).Journal of Infectious Diseases,126, 345–347.
4. Brown, R. D. &Scott, G. R. (1960).Veterinary Record,72, 1055–1056.
5. Diaz, A. M. O. &Varela-Diaz, V. M. (1976).Zentralblatt für Bakteriologie, Parasitenkunde, Infektionskrankheiten und Hygiene, Abt. I. Orig.,A236, 185–190.