Vessel and shipowner liability in collisions or other maritime casualties : hearings before the Merchant Marine and Fisheries Subcommittee of the Committee on Commerce, United States Senate, Eighty-eighth Congress, first session, on S. 555, a bill to unify apportionment of liability in cases of collision between vessels, and in other maritime casualties; S. 556, a bill to limit the liability of shipowners, and for other purposes, May 20 and 22, 1963