@Inproceedings{EPTCS4.2,
  author    = {Tveretina, Olga and Sinz, Carsten and Zantema, Hans },
  year      = {2009},
  title     = {An Exponential Lower Bound on OBDD Refutations for Pigeonhole Formulas},
  editor    = {Markakis, Evangelos and Milis, Ioannis},
  booktitle = {{\rm Proceedings Fourth Athens Colloquium on}
               Algorithms and Complexity,
               {\rm Athens, Greece, August 20-21, 2009}},
  series    = {Electronic Proceedings in Theoretical Computer Science},
  volume    = {4},
  publisher = {Open Publishing Association},
  pages     = {13-21},
  doi       = {10.4204/EPTCS.4.2},
}