1. Kolle, Kraus, Uhlenhuth;R. Abel,1929
2. Belfanti, S. andDella Vedova. 1896. Giorn. Acad. med. Torino2, 149.
3. Coglia, L. 1946. Annali d’Igiene No 6.
4. Frobisher, M., Parsons, E. I. andUpdyke, E. 1947. Am. J. Publ. Health37, 543.
5. Frobisher, M. 1946. Fundamentals of Bacteriology. Saunders, Philadelphia-Londen.