1. DC Blood, and OM Radostits (1986 ) InVeterinary Medicine , 6th edn , Lea and Febiger, Philadelphia, p658 .
2. O. Bollinger, and MT Rosen (1878 ) quoted by (1878 ).
3. GR Carter, and NR Krieg (1984 ) InBergeys Manual of Systemic Bacteriology , Vol 1 , Williams and Wilkins, Baltimore, p552 .