1. The gingival pocket. Anatomy, pathology, deepening and elimination;Waerhaug;Odontologisk Tidsskrift,1952
2. Incidence of clinical manifestations of periodontal disease in light of oral hygiene and calculus formation;Lövdal;J Am Dent Assoc,1958
3. Alveolar bone loss as related to oral hygiene and age;Schei;J Perio,1959
4. Oral hygiene and periodontal disease;Greene;Am J Public Health,1963
5. Waerhaug J. Epidemiology of periodontal disease. In: Ramfjord SF, Kerr D A, Ash M M. (eds). Workshop in periodontology, 1966 pp179–211.