@inproceedings{ijcai1989p199,
  title     = {Approximation of Indistinct Concepts},
  author    = {Zhang, Mingyi},
  booktitle = {Proceedings of the Eleventh International Joint Conference on
               Artificial Intelligence, {IJCAI-89}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {N. S. Sridharan},
  pages     = {1244--1247},
  year      = {1989},
  month     = {8},
  note      = {Knowledge Representation},
  url       = {https://ijcai.org/proceedings/1989/199},
}