@article{d2decentralizedtrainingoverdecentralized,
  title = {D$^2$: Decentralized Training over Decentralized Data},
  author = {Hanlin Tang and Xiangru Lian and Ming Yan and Ce Zhang and Ji Liu},
  year = {2018},
  eprint = {1803.07068},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1803.07068v2},
}