@article{Lang-Liberatore-Marquis-03,
  author    = {J{\'e}r{\^o}me Lang and
               Paolo Liberatore and
               Pierre Marquis},
  title     = {Propositional Independence: Formula-Variable Independence and Forgetting},
  journal   = {Journal of Artificial Intelligence Research (JAIR)},
  volume    = {18},
  pages     = {391--443},
  year      = {2003},
}