Complex sentence: In April 2004, CNOOC-SINOPEC United International Trading was granted a license to import crude oil by the Ministry of Commerce in an unprecedented measure, since CNPC, Sinopec, Sinochem and Zhuhai Zhenrong used to be the only companies which imported crude oil to China.
Split into simpler sentences: In April 2004, the Ministry of Commerce granted CNOOC-SINOPEC United International Trading a license to import crude oil. Previously, CNPC, Sinopec, Sinochem and Zhuhai Zhenrong had been the only companies which imported crude oil to China.