Hong Tian Zhao Pixi Xiukun Wang CRST: A Generalization of Rough Set Theory. 364-372 2005 conf/rsfdgrc/2005-1 RSFDGrC (1) http://dx.doi.org/10.1007/11548669_38 db/conf/rsfdgrc/rsfdgrc2005-1.html#TianPW05