006350000a22001570004500003000900000005001700009110010800026245016400134020001800298264004900316490004000365300000900405041000800414650002500422700003000447PH-MaWHO20241108112340.0 aWHO Scientific Group on Epidemiology, Etiology, and Prevention of Periodontal Diseases (1977 : Moscow). aEpidemiology, etiology, and prevention of periodontal diseases : report of a WHO scientific group [meeting held in Moscow from 23 November to 2 December 1977]. a92-4-120621-7 aGeneva : bWorld Health Organization,c1978. a(WHO technical report series ; 621) a60p. aeng aPeriodontal diseases aWorld Health Organization