@article{mones2014hierarchy,
  title={Universal hierarchical behavior of citation networks},
  author={Mones, Enys and Pollner,  Peter and Vicsek, Tamas},
  journal={Journal of Statistical Mechanics: Theory and Experiment},
  volume={2014},
  number={5},
  pages={P05023},
  url={http://stacks.iop.org/1742-5468/2014/i=5/a=P05023},
  year={2014},
}