Roughness of Type-2 Fuzzy Set Based on Similarity Relation. - Haoyang Wu; Yuyuan Wu; Haitao Liu; Hongjun Zhang (Int. J. Uncertain. Fuzziness Knowl. Based Syst., 2007)

An Interval Type-2 Fuzzy Rough Set Model for Attribute Reduction. - Haoyang Wu; Yuyuan Wu; Jinping Luo (IEEE Trans. Fuzzy Syst., 2009)