1Sun Zuchen and Huang Zhiqian (China Petroleum Material & Equipment Corporation, CNPC).Recent R & D in Drilling Equipment[J].China Oil & Gas,1997,4(3):153-155.
2(Continued from last issue)Sun Zuchen(China Petroleum Material & Equipment Corporation, CNPC).Recent R&D in Drilling Equipment[J].China Oil & Gas,1997,4(4):223-224.