@article{palla2007quantifying,
  author = {Palla, Gergely and Barabási, Albert-lászló and Vicsek, Tamás and Hungary, Budapest},
  interhash = {911359764769215213b2d31dc6394078},
  intrahash = {9c5a50822cb5580b66a7371b833bb2fe},
  pages = 2007,
  title = {Quantifying social group evolution},
  url = {http://130.203.133.150/viewdoc/summary?doi=10.1.1.119.7541},
  volume = 446,
  year = 2007
}

@article{schein70,
  author = {Plemmons, R. J. and Schein, B. M.},
  interhash = {341ee2f65ff1940a18d395f2cf5eadd4},
  intrahash = {100395cf400ac7fa3109ce84ae9bcdb8},
  journal = {Semigroup Forum},
  pages = {267-271},
  title = {Groups of Binary Relations},
  volume = 1,
  year = 1970
}