Yan Zhao S. K. Michael Wong Y. Y. Yao A Note on Attribute Reduction in the Decision-Theoretic Rough Set Model. 61-70 2008 RSCTC http://dx.doi.org/10.1007/978-3-540-88425-5_7 conf/rsctc/2008 db/conf/rsctc/rsctc2008.html#ZhaoWY08