@ARTICLE{Jenatton2011,
  author = {Jenatton, R. and Mairal, J. and Obozinski, G. and Bach, F.},
  title = {Proximal Methods for Hierachichal Sparse Coding},
  journal = {Journal of Machine Learning Research},
  year = {2011},
  volume = {12},
  pages = {2297--2334},
}