added three_buffersN, print3;
tuned theory_to_proof: plain Proof.state instead of history;
added EXCEPTION;
removed DATA_FAIL, TRANSLATION_FAIL;
\index{model checking example|(}%
\index{lfp@{\texttt{lfp}}!applications of|see{CTL}}
\input{CTL/document/Base.tex}
\input{CTL/document/PDL.tex}
\input{CTL/document/CTL.tex}
\index{model checking example|)}