Opposition to the resumption of specie convertibility of the Greenbacks during 1879 was accordingly muted. Free trade relied on the free convertibility of currencies. The liberalization and opening of the capital opening culminated in full-peso convertibility in 1992. Hanke wrote many articles showing that the Convertibility System was not a currency board. This caused deflation but allowed the Bank to resume full convertibility in 1821. In 1971 the U.S. government suspended the convertibility of the U.S. dollar to gold. It also guaranteed full convertibility of pesos into U.S. dollars. By 1947, rationing had to be tightened and the convertibility of the pound suspended. Menem supported the Washington Consensus, and tackled inflation with the Convertibility plan in 1991. President Nixon cancelled the fixed-rate convertibility of US dollars to gold in 1971. Type theory is chiefly interested in the convertibility or reducibility of programs. Marx tends to assume the convertibility of paper money into gold. The responsibility of the free convertibility remained in the French Treasury. However, gold convertibility did not resume. Gold convertibility enforcement was not required, but instead, allowed.