@article{6:46,author={Arindam Banerjee and Inderjit S. Dhillon and Joydeep Ghosh and Suvrit Sra}, Title={Clustering on the Unit Hypersphere using von Mises-Fisher  Distributions},journal={Journal of Machine Learning Research},volume={6}, url={http://www.jmlr.org/papers/volume6/banerjee05a/banerjee05a.pdf}}