@article{GabowT85,
  title={A linear-time algorithm for a special case of disjoint set union},
  author={Gabow, H.N. and Tarjan, R.E.},
  journal={Journal of computer and system sciences},
  volume={30},
  number={2},
  pages={209--221},
  year={1985},
  publisher={Elsevier}
}