\begin{thebibliography}{1}

\bibitem{bar-hillel}
Y.~Bar-Hillel, M.~Perles, and E.~Shamir.
\newblock On formal properties of simple phrase structure grammars.
\newblock {\em Zeitschrift f{\"u}r Phonetik, SprachWissenschaft und
  Kommunicationsforschung}, 14:143--172, 1961.
\newblock Reprinted in Bar-Hillel's Language and Information -- Selected Essays
  on their Theory and Application, Addison Wesley series in Logic, 1964, pp.
  116-150.

\bibitem{billot-lang}
S.~Billot and B.~Lang.
\newblock The structure of shared parse forests in ambiguous parsing.
\newblock In {\em 27th Annual Meeting of the Association for Computational
  Linguistics}, pages 143--151, Vancouver, 1989.

\bibitem{hopcroft-ullman}
John~E. Hopcroft and Jeffrey~D. Ullman.
\newblock {\em Introduction to Automata Theory, Languages and Computation}.
\newblock Addison Wesley, 1979.

\bibitem{lang74}
Bernard Lang.
\newblock Deterministic techniques for efficient non-deterministic parsers.
\newblock In J.~Loeckx, editor, {\em Proceedings of the Second Colloquium on
  Automata, Languages and Programming}, 1974.
\newblock Also: Rapport de Recherche 72, IRIA-Laboria, Rocquencourt (France).

\bibitem{dcg}
Fernando C.~N. Pereira and David Warren.
\newblock Definite clause grammars for language analysis --- a survey of the
  formalism and a comparison with augmented transition networks.
\newblock {\em Artificial Intelligence}, 13, 1980.

\end{thebibliography}
