(a) in the case of tariff headings on which the duties applied in practice on 1 January 1957 do not differ by more than 15% in either direction from the duties in the Common Customs Tariff, the latter duties shall be ap plied at the end of the fourth year after the entry into force of this Treaty;
(a) i gcás na gceannteideal taraife nach bhfuil na dleachtanna a bhí á bhfeidhmiú orthu iarbhir ar an I Eanáir 1957 thar 15% nios mó nó níos lú ná na dleachtanna sa Chomhtharaif Chustaim, cuirfear na dleachtanna deiridh sin chun feidhme ag deireadh an cheathrú bliain tar éis an Conradh seo a theacht i bhfeidhm;