added lemmas irreflp_{less,greater} to preorder and {trans,irrefl}_mult{,p} to Multiset
\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|)}