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2. National trends in the prevalence and severity of the periodontal diseases;Douglass;JADA,1983
3. The periodontal status of boys 11 to 17 years old in Bombay, India;Ramfjord;J Periodontol,1961
4. Periodontal disease among naval recruits;Wirthlin;US Navy Medicine,1981
5. Proceedings from World Workshop in Periodontics, 1966;Ramfjord,1966