@article{lee2011unsupervised,
  title={Unsupervised learning of hierarchical representations with convolutional deep belief networks},
  author={Honglak Lee and Roger Grosse and Rajesh Ranganath and A.~Y. Ng},
  journal={Communications of the ACM},
  volume={54},
  number={10},
  pages={95--103},
  year={2011},
  publisher={ACM}
}