Air pollution : hearings before a subcommittee of the Committee on Interstate and Foreign Commerce, House of Representative, 84th Congress, first session on H. R. 4415, H. R. 4750, bills to improve, strengthen, and accelerate programs for the prevention and abatement of air pollution, H. R. 3507, H. R. 4061, bills to accelerate, extend, and strengthen the federal air pollution control program, Mar. 18 and 19, 1963.