WHO's first assisting? A patchwork of payment for first assistants.
D003406:Credentialing; D003625:Data Collection; D007349:Insurance, Health, Reimbursement; D009871:Operating Room Nursing / Q000191:economics* / Q000193:education / Q000592:standards; D009872:Operating Room Technicians / Q000191:economics* / Q000592:standards; D014481:United States