...time.

8#8Department of Computer Science, Stanford University, Stanford, CA 94305. Research supported in part by ONR Young Investigator Award N00014-91-J-1855, by NSF Presidential Young Investigator Grant CCR-8858097 with matching funds from AT&T and DEC, Stanford University Office of Technology Licensing, by a grant form Mitsubishi Corp, and by NEC Research Institute.

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...time.

9#9NEC Research Institute, Princeton NJ 08540.

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...time.

10#10Department of Computer Science, Stanford University, Stanford, CA 94305. Research supported by NSF Research Initiation Award CCR-900-8226, by U.S. Army Research Office Grant DAAL-03-91-G-0102, by a grant from Mitsubishi Electric Laboratories, and by NEC Research Institute.

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...permutations

Throughout this paper, 12#12 denotes 13#13.

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