Seminar on the radiological burden of man from natural radioactivity in the countries of the European Communities, Le Vesinet, Paris, 4-6 December 1979. Seminar organized by the Directorate-General Employment and Social Affairs Health and Safety Directorate and the Directorate-General Research, Science and Education Biology, Radiation Protection and Medical Research Programme, in collaboration with the Service Central de Protection contre les Rayonnements lonisants (SCPRI), Le Vesinet, Paris. February, 1980