... Johnson 1
  Published in ACM SIGACT News, December 1998.

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... \author 2
  Dipartimento di Sistemi ed Informatica, Università di Firenze, Via Cesare Lombroso 6/17, 50134 Firenze, Italy, `piluc@dsi.unifi.it`

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... \author 3
  Department of Numerical Analysis and Computing Science, Royal Institute of Technology, SE-100 44 Stockholm, Sweden, `viggo@nada.kth.se`
  Copyright © Pierluigi Crescenzi and Viggo Kann, 1998

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