The problems facing the historical research worker.
D001680:Biographies as Topic; D003754:Dental High-Speed Equipment / Q000266:history; D006665:History of Dentistry; D049669:History, 16th Century; D049672:History, 19th Century; D049673:History, 20th Century; D049690:History, Ancient; D010158:Palatal Obturators / Q000266:history; D012106:Research; D006113:United Kingdom; D014956:Writing