@article{pollner2006preferential,
  title={Preferential attachment of communities: The same principle, but a higher level},
  author={Pollner, Peter and Palla, Gergely and Vicsek, Tamas},
  journal={EPL (Europhysics Letters)},
  volume={73},
  number={3},
  pages={478},
  year={2006},
  publisher={IOP Publishing}
}