@article{cj95-04,
  author={Anne Condon and Joan Feigenbaum and Carsten Lund and
          Peter W. Shor},
  title={Probabilistically Checkable Proof Systems and
         Nonapproximability of
         \protect\(\textsl{PSPACE}\protect\)-Hard Functions},
  journal={Chicago Journal of Theoretical Computer Science},
  volume={1995},
  number={4},
  publisher={MIT Press},
  month={October},
  year={1995}
}