@article{czirok1999collective,
  title={Collective motion of organisms in three dimensions},
  author={Czir{\'o}k, Andr{\'a}s and Vicsek, M{\'a}ria and Vicsek, Tam{\'a}s},
  journal={Physica A: Statistical Mechanics and its Applications},
  volume={264},
  number={1},
  pages={299--304},
  year={1999},
  publisher={North-Holland}
}