@article{Tarjan79,
  author    = {Robert Endre Tarjan},
  title     = {A Class of Algorithms which Require Nonlinear Time to Maintain
               Disjoint Sets},
  journal   = {J. Comput. Syst. Sci.},
  volume    = {18},
  number    = {2},
  year      = {1979},
  pages     = {110--127},
  ee        = {http://dx.doi.org/10.1016/0022-0000(79)90042-4},
}