\providecommand{\bysame}{\leavevmode\hbox to3em{\hrulefill}\thinspace}
\providecommand{\MR}{\relax\ifhmode\unskip\space\fi MR }
% \MRhref is called by the amsart/book/proc definition of \MR.
\providecommand{\MRhref}[2]{%
  \href{http://www.ams.org/mathscinet-getitem?mr=#1}{#2}
}
\providecommand{\href}[2]{#2}
\begin{thebibliography}{1}

\bibitem{curry:foundations}
Haskell~B. Curry, \emph{Foundations of mathematical logic}, Dover Publications,
  Inc., 1977.

\bibitem{gs:discretemaths}
David Gries and Fred B.Schneider, \emph{A logical approach to discrete
  mathematics}, Springer-Verlag, 1993.

\bibitem{kleene:meta52}
Stephen~Cole Kleene, \emph{Introduction to metamathematics}, North-Holland
  Publishing CO., 1964.

\bibitem{szabo:gentzen}
M.~Szabo (ed.), \emph{The collected papers of {G}erhard {G}entzen},
  North-Holland, Amsterdam, 1969.

\end{thebibliography}
