\documentclass[10pt,a4paper,twocolumn]{article}

\usepackage[margin=2cm]{geometry}

\usepackage{enumitem}
\setenumerate[1]{label=\alph*)}

% textcomp package is not available everywhere, and we only need the Copyright symbol
% taken from http://tex.stackexchange.com/a/1677/23992
\DeclareTextCommandDefault{\textregistered}{\textcircled{\check@mathfonts\fontsize\sf@size\z@\math@fontsfalse\selectfont R}}

\usepackage{fancyhdr}
\renewcommand{\headrulewidth}{0pt}
\renewcommand{\footrulewidth}{0pt}
\fancyhead{}
\fancyfoot[C]{Copyright \textcopyright 2015 Camil Staps}
\pagestyle{fancy}

\usepackage{tikz}
\usetikzlibrary{positioning,arrows,automata}

\usepackage{amsmath}

% Solution environment
\newenvironment{solution}[1]{\medskip\noindent{\textbf{Exercise \thesection.#1}\rm\par}{\medskip}}

\parindent0pt

\title{Solutions to selected exercises from Thomas Sudkamp, \textit{Languages and Machines} (second edition)}
\author{Camil Staps}

\begin{document}

\maketitle

\setcounter{section}{8}
\section{Turing machines}
\input{ex9-1.tex}
\input{ex9-2.tex}
\input{ex9-3.tex}
\input{ex9-4.tex}

\end{document}