1. Rivers, T. M., and Norfall, F. J., Viral and Rickettsial Infections of Man, third ed. (Lippincott, Philadelphia, 1959).
2. Gardner, P. S., Wright, A. E., and Hale, J. H., Brit. Med. J., 2, 424 (1961).
3. Paul, J. R., et al., Amer. J. Hyg., 54, 275 (1961).
4. Downie, A. W., et al., Bull. World Health Org., 25, 55 (1961).
5. Mastyucova, J. N., and Jaroslavskava, H. W., Voprosi Virusologii, 1, 67 (1961).