Airspace, space rental, and health services improvement : hearing, Ninety-first Congress, second session on S. 3647, to authorize the Commissioner of the District of Columbia to lease airspace above and below freeway rights-of-way within the District of Columbia, and for other purposes : S. 3648, to provide improvements in the Administration of Health Services in the District of Columbia, and for other purposes : S. 3649, relating to the rental of space for the accommodation of District of Columbia agencies and activities, and for other purposes, April 2, 1970.