Columbia subject headings:
Medical care--United States--Cost effectiveness.
Midwives--United States.
Nurse practitioners--United States.
Physicians' assistants--United States.
Harvard subject headings:
Medical care--United States--Cost effectiveness
Midwives--United States
Nurse practitioners--United States
Physicians' assistants--United States
Princeton subject headings:
Medical care--United States--Cost effectiveness.
Midwives--United States.
Nurse practitioners--United States.
Physicians' assistants--United States.