tikz で有向グラフを記述する LaTeX サンプルコードを作ってみました．サンプルではリンク間の距離が無駄に長いので，ノードの座標を修正する代わりに53行目で座標のみスケールを 1/2 にしています．

\documentclass{standalone}
\usepackage{tikz}\usetikzlibrary{arrows,calc}
\begin{document}
% ========================================
% setting
% ========================================
% node/link/link label style
\tikzstyle{node}=[draw=black,circle,inner sep=0,minimum size=20]
\tikzstyle{link}=[->,very thick,bend left=20]
\tikzstyle{link_label}=[draw=none,thin,inner sep=5,fill=white]

% node coordinate data (format:nodeID/x/y)
\def \nodes {
  1/ 6/18,
  2/ 6/12,
  3/13/12,
  4/ 4/ 6,
  5/20/12,
  6/14/ 6,
  7/ 0/ 0,
  8/20/ 6,
  9/15/ 0%
}

% link connection data (format:linkID/fromID/toID)
\def \links{
  a/1/2,
  b/2/3,
  c/2/4,
  d/3/5,
  e/3/6,
  f/4/6,
  g/4/2,
  h/4/7,
  i/6/8,
  j/6/4,
  k/6/3,
  l/6/9%
}

% ========================================
% drawing
% ========================================
\begin{tikzpicture}[scale=.5]
  % node coordinates
  \foreach \nodeID/\x/\y in \nodes { 
    \node [node] (node_\nodeID) at (\x,\y)
    {\nodeID}; 
  }
  % link road link and its representative points
  \foreach \linkID/\fromNode/\toNode in \links {
    \draw (node_\fromNode) edge [link] 
    node [link_label] {$\linkID$}
    (node_\toNode); 
  }
\end{tikzpicture}
\end{document}

directed_graph