src/HOL/IMP/document/root.tex

clarified code setup

\documentclass[11pt,a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage{amssymb}
\usepackage{isabelle,isabellesym}
\usepackage{latexsym}
% this should be the last package used
\usepackage{pdfsetup}

% snip
\newcommand{\repeatisanl}[1]{\ifnum#1=0\else\isanewline\repeatisanl{\numexpr#1-1}\fi}
\newcommand{\snip}[4]{\repeatisanl#2#4\repeatisanl#3}

\urlstyle{rm}
\isabellestyle{it}

\renewcommand{\isacharunderscore}{\_}
\renewcommand{\isacharunderscorekeyword}{\_}

% for uniform font size
\renewcommand{\isastyle}{\isastyleminor}

\begin{document}

\title{Concrete Semantics}
\author{Tobias Nipkow \& Gerwin Klein}
\maketitle

\begin{abstract}
This document presents formalizations of the semantics of a simple imperative programming language together with a number of applications: a compiler, type systems, various program analyses and abstract interpreters. These theories form the basis of the book \emph{Concrete Semantics with Isabelle/HOL} by Nipkow and Klein \cite{NipkowK2014}.
\end{abstract}

\setcounter{tocdepth}{2}
\tableofcontents
\newpage

% generated text of all theories
\input{session}

\nocite{Nipkow}
\nocite{ConcreteSemantics}

\bibliographystyle{abbrv}
\bibliography{root}

\end{document}