Health maintenance organizations--1973 : hearings before the Subcommittee on Public Health and Environment of the Committee on Interstate and Foreign Commerce, House of Representatives, Ninety-third Congress, first session on H.R. 51 and H.R. 4871, bills to amend the Public Health Service Act to provide assistance and encouragement for the establishment and expansion of health maintenance organizations, and for other purposes, March 6 and 7, 1973