@article{czirok2000collective,
  title={Collective behavior of interacting self-propelled particles},
  author={Czir{\'o}k, Andr{\'a}s and Vicsek, Tam{\'a}s},
  journal={Physica A: Statistical Mechanics and its Applications},
  volume={281},
  number={1},
  pages={17--29},
  year={2000},
  publisher={Elsevier}
}