title: Emergency medical services: a journey to subspecialty.
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Delbridge
authors.forename: Debra G
authors.initials: DG
authors.lastname: Perina
mesh_terms: D004632:Emergency Medical Services / Q000458:organization & administration* / Q000639:trends; D006801:Humans; D008511:Medicine / Q000458:organization & administration* / Q000639:trends; D024382:Professional Role; D014481:United States