@article{farkas2002segregation,
  title={Segregation of granular binary mixtures by a ratchet mechanism},
  author={Farkas, Z{\'e}n{\'o} and Szalai, Ferenc and Wolf, Dietrich E and Vicsek, Tam{\'a}s},
  journal={Physical Review E},
  volume={65},
  number={2},
  pages={022301},
  year={2002},
  publisher={APS}
}