M
[MS72] Albert R. Meyer and Larry J. Stockmeyer. The Equivalence Problem for Regular Expressions with Squaring Requires Exponential Space. In FOCS'72, pages 125-129. IEEE Comp. Soc. Press, October 1972. 
@inproceedings{focs1972-MS,
  author =              {Meyer, Albert R. and Stockmeyer, Larry J.},
  title =               {The Equivalence Problem for Regular Expressions with
                         Squaring Requires Exponential Space},
  booktitle =           {{P}roceedings of the 13th {A}nnual {S}ymposium on
                         {F}oundations of {C}omputer {S}cience ({FOCS}'72)},
  acronym =             {{FOCS}'72},
  publisher =           {IEEE Comp. Soc. Press},
  pages =               {125-129},
  year =                {1972},
  month =               oct,
}
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