@inproceedings{thevariationalhierarchicalemalgorithmfor,
  title = {The variational hierarchical EM algorithm for clustering hidden Markov models},
  author = {Emanuele Coviello and Gert R. Lanckriet and Antoni B. Chan},
  year = {2012},
  booktitle = {NeurIPS 2012 12},
  url = {http://papers.nips.cc/paper/4779-the-variational-hierarchical-em-algorithm-for-clustering-hidden-markov-models},
}