@article{switching pigeons,
  author={ Zhao Cheng, and Zhiyong Chen, and Tamás Vicsek, and Duxin Chen, and  HHai-Tao Zhang},
  title={Switching hierarchical leadership mechanism in homing flight of pigeon flocks},
  journal={Europhys. Lett.},
  volume={114},
  number={},
  pages={60008},
  url={https://www.dovepress.com/articles.php?article_id=27635},
  year={2016},
}