International financial conditions : hearings before the Subcommittee on International Finance of the Committee on Banking, Housing, and Urban Affairs, United States Senate, Ninety-Sixth Congress, first session on the effects of blockage of Iranian assets; the use of the dollar as an international currency; the implication of OPEC oil price increases; the competitive position of U.S. banks; gold; special drawing rights; substitution accounts; and foreign exchange trading, December 12 and 14, 1979