1. Hypodontia in the permanent dentition;Grahnén;Odontol Revy,1956
2. Hypodontia of permanent teeth;Haavikko;Suom Hammaslääk Toim,1971
3. Congenital numerical variation in the permanent dentition;Egermark-Eriksson;Odontol Revy,1971
4. An orthopantomographic study of hypodontia, supernumeraries and other anomalies in school children between the ages of 8-9 years;Bergström;Swed Dent J,1977
5. Hypodontia of permanent teeth in Danish schoolchildren;Rølling;Scand J Dent Res,1980