INTERNATIONAL 528,409 International Symposium on Requirements for Poultry Virus Vaccines.Proceedings of the 42th Symposium.Org. by the International Association of Biological Standardization and held at the Supérieure de Commerce fif Lyon /France/.Acting ed. ; Ch. Merieux /et al, Basel 1974 S.Karger 8° s. XII, 445, il Developments in Biological Standardization vol. 25