Rubber example

mydoc.tex

\documentclass{book}

\usepackage{lipsum}
\usepackage{makeidx}

\makeindex

\begin{document}

\title{My first book}
\author{Paulo}
\date{\today}

\maketitle

\tableofcontents

\chapter{Hello world}
\label{chap:hw}

\lipsum[1]

\section{Hello John}
\label{sec:hj}

\lipsum[2-4]

\section{Hello Mary}
\label{sec:hm}

\lipsum[3-6]

John\index{Friends!John} said hello in Section~\ref{sec:hj}.

\chapter{Goodbye world}
\label{chap:gbw}

\lipsum[10]

In Chapter~\ref{chap:hw}, we said hello. Now it is time to say goodbye.

\section{Goodbye John}
\label{sec:gbj}

\lipsum[12-15]

Thanks Mary\index{Friends!Mary}. I know you will say goodbye in Section~\ref{sec:gbm}.

\section{Goodbye Mary}
\label{sec:gbm}

\lipsum[16-19]

\printindex

\end{document}