make WWW_Find work again, now that its ML modules reside within a theory context (cf. bf5b45870110) -- patch by Rafal Kolanski;
\index{model checking example|(}%
\index{lfp@{\texttt{lfp}}!applications of|see{CTL}}
\input{Base.tex}
\input{PDL.tex}
\input{CTL.tex}
\index{model checking example|)}