clarified NEWS: document_files are officially required since Isabelle2014, but the absence was tolerated as legacy feature;
\documentclass[11pt,a4paper]{article}
\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
\setcounter{tocdepth}{2}
\tableofcontents
\newpage
% generated text of all theories
\input{session}
\nocite{Nipkow}
\nocite{ConcreteSemantics}
\bibliographystyle{abbrv}
\bibliography{root}
\end{document}