NCHSR /NATIONAL CENTER FOR HEALTH SERVICES RESEARCH/. RESEARCH SUMMARY SERIES 604,358 NURSE Nurse practitioners and physician assistants: a research agenda. Summary of the proceedings of a conference held June 21-22, 1977, Warrenton, Virginia December 1978. Hyatsville 1979 U.S.Department of Health Education and Welfare 8° s. 20 NCHSR National Center for Health Services Research. Research Summary ser.