@article{xu2020opportunistic,
  author={Xu, Ran and Li, Yong and Chen, Sheng},
  journal={IEEE Transactions on Big Data (ToB)},
  title={On the Opportunistic Topology of Taxi Networks in Urban Mobility Environment},
  year={2020},
  volume={6},
  number={1},
  pages={171-188},
  publisher={IEEE}
}