% de naeste seks makroer anvendes internt
% de kan uden problemer fjernes i hele filen
\let\START\relax
\let\STOP\relax
\let\SPECEXTSTART\relax
\let\SPECEXTSTOP\relax
\let\DCBEGIN\relax
\let\DCEND\relax
 \DCBEGIN
\documentclass[a4paper]{article}
 \DCEND

 \usepackage [latin1]{inputenc}
 \usepackage [T1]{fontenc}
 \usepackage [danish]{babel}
 \usepackage {felineekssupp}
 \usepackage {kpfonts}
 \usepackage [scaled=0.8]{beramono}
 \usepackage [scaled=0.85]{berasans}

% al anvendelse af geometry i eksemplerne boer man slette,
% dette anvendes mht. at stoerrelsen skal passe til brug i bogen
\usepackage{geometry}
\geometry{textwidth=386.5pt}
% vil ikke have sidetal med, fjern selv
\pagestyle{empty}
% forfatteren snyder maaske, fjern kode fra HER -->

% <-- til HER.
 \START
\usepackage{tikz}
 \STOP

\begin{document}
\tikzstyle{knude}=[circle,draw=blue!50,fill=blue!20,thick]
\begin{tikzpicture}[shorten >=2pt]
  \node (a_1) at (0,0)       [knude] {$a_1$};
  \node (a_2) at (1,2)       [knude] {$a_2$};
  \node (a_3) at (2.5,1)     [knude] {$a_3$};
  \node (a_4) at (4,2)       [knude] {$a_4$};
  \node (a_5) at (5,0)       [knude] {$a_5$};
  \node (a_6) at (1.5,-1.25) [knude] {$a_6$};
  \node (a_7) at (4,-1.25)   [knude] {$a_7$};

  \draw[->] (a_1) -- node [auto,swap]  {5}                       (a_2);
  \draw[->] (a_2) -- node [auto] {3} (a_4) -- node [auto] {$-2$} (a_5);
  \draw[->] (a_2) -- node [auto,swap] {12}                       (a_3);
  \draw[->] (a_3) -- node [auto,swap] {0}                        (a_4);
  \draw[->] (a_1) -- node [auto] {$x$} (a_6) --                  (a_5);
  \draw[->,dashed]    (a_7) --                                   (a_5);
  \draw[->,red,thick] (a_1) to  [out=0,in=-100]                  (a_4);
\end{tikzpicture}
\end{document}