Isotopes and radiation in parasitology 4 : proceedings of an Advisory Group Meeting on the Immunology and Pathogenesis of Parasitic Infections in Ruminants and the Influence of Genetic and Nutritional Factors organized by the joint FAO/IAEA division of Atomic Energy in Food and Agriculture and held in Cambridge from 10 to 14 September 1979 (International Atomic Energy Agency, 1981)