title: Specialization, subspecialization, and subsubspecialization in internal medicine.
authors.affiliation: American Board of Internal Medicine, Philadelphia, USA.
authors.forename: Christine K
authors.initials: CK
authors.lastname: Cassel
authors.forename: David B
authors.initials: DB
authors.lastname: Reuben
mesh_terms: D002568:Certification / Q000266:history / Q000592:standards; D049673:History, 20th Century; D007388:Internal Medicine / Q000592:standards; D013038:Specialization / Q000266:history / Q000592:standards; D013044:Specialty Boards; D014481:United States