@article{czirok1998exponential,
  title={Exponential distribution of locomotion activity in cell cultures},
  author={Czir{\'o}k, Andr{\'a}s and Schlett, Katalin and Madar{\'a}sz, Em{\'\i}lia and Vicsek, Tam{\'a}s},
  journal={Physical Review Letters},
  volume={81},
  number={14},
  pages={3038},
  year={1998},
  publisher={American Physical Society}
}