organized jointly by the CEC and the Institute for Soil Fertility, Haren (Gr.), and held in Groningen, Netherlands, on June 12 and 13, 1980 ; sponsored by the Commission of the European Communities, Directorate-General for Agriculture, and Directorate-General for Research, Science and Education ; edited by T.W.G. Hucker and G. CatrouxD. Reidel Pub. Co.c1981