1. Lee, D.D., Seung, H.S.: Learning the parts of objects by non-negative matrix factorization. Nature 401, 788–791 (1999)
2. Lee, D.D., Seung, H.S.: Algorithms for non-negative matrix factorization. In: Advances in Neural Information Processing 13. Proc. NIPS 2000, MIT Press, Cambridge (2001)
3. Xu, W., Liu, X., Gong, Y.: Document-Clustering based on Non-Negative Matrix Factorization. In: Proceedings of SIGIR 2003, Toronto, CA, July 28-August 1, 2003, pp. 267–273 (2003)
4. Willett, P.: Document clustering using an inverted file approach. Journal of Information Science 2, 223–231 (1990)
5. Baker, L., McCallum, A.: Distributional clustering of words for text classification. In: Proceedings of ACM SIGIR (1998)