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Michael Barr and Charles Wells. 
Toposes, Triples and Theories.
Springer-Verlag, 1983, or see
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\bibitem{prfs}
Jeremy Dawson.
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\url{http://users.rsise.anu.edu.au/~jeremy/isabelle/monad/}.

% \bibitem{hinze-monadic}
% Ralf Hinze. Monadic-style backtracking. Technical Report IAI-TR-96-9,
% Institut fur Informatik III, Universitat Bonn, October 1996.

\bibitem{jones-composing}
Mark P. Jones and Luc Duponcheel, Composing Monads,
Research Report YALEU/DCS/RR-1004, Yale University, December 1993

\bibitem{lhj} Sheng Liang, Paul Hudak, and Mark P Jones.
Monad Transformers and Modular Interpreters.
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\bibitem{maclane-categories} Saunders MacLane.
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Graduate Texts in Mathematics, Springer, 1971.

\bibitem{manes} Ernest G~Manes.  Algebraic theories.
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\bibitem{moggi} Eugenio Moggi.  
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\bibitem{wadler-essence} Philip Wadler. The Essence of Functional Programming.
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\bibitem{wadler-free}
Philip Wadler.  Theorems for free!
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Computer Architecture, ACM Press, 1989, 347--359. 


\end{thebibliography}