title: Emergency medical service systems: a concept whose time has come.
mesh_terms: D004632:Emergency Medical Services / Q000266:history; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D008887:Military Medicine / Q000266:history; D013041:Specialties, Nursing; D014187:Transportation of Patients; D014481:United States