Purchase and charter of foreign merchant vessels for national defense : hearings before the Committee on Commerce, United States Senate, Seventy-seventh Congress, first session, on S.J. Res. 67, a joint resolution authorizing the purchase of foreign merchant vessels for national defense, and for other purposes, and H.R. 4466, an act to authorize the acquisition by the United States of title to or the use of domestic or foreign merchant vessels for urgent needs of commerce and national defense, and for other purposes