\documentclass[a4paper]{article}
\usepackage{isolatin1}
\usepackage{amsmath}
\parindent 0mm
\parskip 5pt

\title{The example with even and odd}
\author{Thomas Hallgren}

\begin{document}
\maketitle

\section{The example with even and odd}

First we define types for truth values and natural numbers.
We then define the two mutually recursive functions $even$ and $odd$.

\input{evenodd.alfa.tex}

\end{document}