@inproceedings{DBLP:conf/focs/Ullman72,
  author    = {Jeffrey D. Ullman},
  title     = {A Fast Algorithm for the Elimination of Common Subexpressions},
  booktitle = {SWAT (FOCS)},
  year      = {1972},
  pages     = {161-176},
  ee        = {http://doi.ieeecomputersociety.org/10.1109/SWAT.1972.1},
  crossref  = {DBLP:conf/focs/FOCS13},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

@proceedings{DBLP:conf/focs/FOCS13,
  title     = {13th Annual Symposium on Switching and Automata Theory,
               College Park, Maryland, USA, October 25-27, 1972},
  booktitle = {SWAT (FOCS)},
  publisher = {IEEE Computer Society},
  year      = {1972},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}