@article{pwlsultraanefficientclusteringand,
  title = {PWLS-ULTRA: An Efficient Clustering and Learning-Based Approach for Low-Dose 3D CT Image Reconstruction},
  author = {Xuehang Zheng and Saiprasad Ravishankar and Yong Long and Jeffrey A. Fessler},
  year = {2017},
  eprint = {1703.09165},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1703.09165v3},
}