Public law 527-559, 77th Congress. Hours of labor. H. R. 4579, act to amend subsec. (c) of sec. 1 of Public numbered 846, 74th Congress, to provide conditions for purchase of supplies and making of contracts by United States [so that provisions of subsec. (c). preventing work in excess of 8 hours in any 1 day or in excess of 40 hours in any 1 week, shall not be applicable to employees of contractors who have entered into annual wage agreements as result of collective bargaining].