@article{DBLP:journals/ijufks/WuWLZ07,
  author    = {Haoyang Wu and
               Yuyuan Wu and
               Haitao Liu and
               Hongjun Zhang},
  title     = {Roughness of Type-2 Fuzzy Set Based on Similarity Relation},
  journal   = {International Journal of Uncertainty, Fuzziness and Knowledge-Based
               Systems},
  volume    = {15},
  number    = {4},
  year      = {2007},
  pages     = {503-517},
  ee        = {http://dx.doi.org/10.1142/S0218488507004820},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}