Mathematical systems theory

, Volume 7, Issue 2, pp 185–192

An infinite hierarchy of intersections of context-free languages

  • Leonard Y. Liu
  • Peter Weiner

DOI: 10.1007/BF01762237

Cite this article as:
Liu, L.Y. & Weiner, P. Math. Systems Theory (1973) 7: 185. doi:10.1007/BF01762237


The class of languages expressible as the intersection ofk context-free languages is shown to be properly contained within the class of languages expressible as the intersection ofk + 1 context-free languages. Hence an infinite hierarchy of classes of languages is exhibited between the class of context-sensitive languages and the class of context-free languages.

Copyright information

© Springer-Verlag New York Inc. 1973

Authors and Affiliations

  • Leonard Y. Liu
    • 1
  • Peter Weiner
    • 2
  1. 1.International Business Machines CorporationYorktown HeightsUSA
  2. 2.Department of Computer ScienceYale UniversityNew HavenUSA

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