@inproceedings{ijcai2009p226,
  title     = {An Efficient Nonnegative Matrix Factorization Approach in Flexible Kernel Space},
  author    = {Zhang, Daoqiang and Liu, Wanquan},
  booktitle = {Proceedings of the Twenty-First International Joint Conference on
               Artificial Intelligence, {IJCAI-09}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Hiroaki Kitano},
  pages     = {1345--1349},
  year      = {2009},
  url       = {https://ijcai.org/proceedings/2009/226},
}