%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-2-58 on page 359.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{159.83385pt}
\setlength\parindent{0pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-node}
\StopShownPreambleCommands
\begin{document}
\begin{pspicture}[showgrid=true](3,3)
  \cnode(0.5,0.5){0.5cm}{A}
  \cnode(2.9,2.9){0.1cm}{B}
  \ncline[linewidth=0.1pt]{<->}{A}{B}
  \ncput{\textcolor{red}{n}}
  \thput{\textcolor{blue}{t}}
\end{pspicture}
\end{document}