Columbia subject headings:
Emergency medical services--Bibliography.
Emergency medical services--Information services--United States--Directories.
Emergency medical services--United States--Biography.
Emergency medical services--United States--Societies, etc.--Directories.
Harvard subject headings:
Emergency medical services--Bibliography.
Emergency medical services--United States--Biography.
Emergency medical services--United States--Information services--Directories.
Emergency medical services--United States--Societies, etc.--Directories.
Princeton subject headings: