@article{he2007mgcd,
  title={{Multigrid Contact Detection Method}},
  author={Kejing He and Shoubin Dong and Zhaoyao Zhou},
  journal={Physical Review E},
  volume={75},
  number={3},
  pages={036710},
  year={2007},
  publisher={American Physical Society},
  doi={10.1103/PhysRevE.75.036710}
}