Xinyu Du Hao Ying Feng Lin Theory of Extended Fuzzy Discrete-Event Systems for Handling Ranges of Knowledge Uncertainties and Subjectivity. 316-328 2009 17 IEEE T. Fuzzy Systems 2 http://dx.doi.org/10.1109/TFUZZ.2008.2011279 db/journals/tfs/tfs17.html#DuYL09