LeXue91a Lengauer:1991:SAP LeXue94 Lengauer:1994:ASA XueLe91b Xue:1991:SCS Xue92c Xue:1992:FSC Xue92b Xue:1992:LRA XueLe92 Xue:1992:SCSa Xue92a Xue:1992:SCSb Xue93b Xue:1993:AAN Xue93a Xue:1993:NFM XueLen94e Xue:1994:ADL Xue94b Xue:1994:ANU Xue95b Xue:1995:CDL Xue94a Xue:1995:CFM