S.K.M., Wong, and Lingras P.. "Representation of qualitative user preference by quantitative belief functions." IEEE Transactions on Knowledge and Data Engineering 6, no. 1 (1994): 72-78.

S.K.M., Wong, Y.Y. Yao, and Bollmann-Sdorra P.. Qualitative fuzzy system structures In 2nd IEEE Int. Conference on Fuzzy Systems. Vol. 2., 1993.