Negotiators from Iran and 6 world powers have adjourned what they called substantive and useful talks on Tehran's nuclear program, saying they will resume April 7th in Vienna. ______________________ 针对伊朗德黑兰核计划展开的所谓具有实质性和有益性的会谈已暂时休会,伊朗和六大国的谈判专家称,会谈将有望于4月7日在维也纳重启._________________________