%Latex
\documentstyle[fleqn,psfig,12pt,pstricks,pst-node,pst-tree]{article}

%\documentclass[fleqn,12pt]{article}
%\usepackage{pstricks,pst-node,pst-tree}
 
%latex2e
%\documentclass{article}
%\usepackage{epsfig,alltt,fancybox}

\setlength{\textwidth}{6.5in}
\setlength{\oddsidemargin}{0in}
\setlength{\textheight}{8.5in}
\setlength{\headheight}{0in}
\setlength{\headsep}{-0.5in}
\setlength{\parindent}{0in} % block style
\setlength{\parskip}{0.3cm}

\newcommand{\mytitle}[1]{\newpage \huge \begin{center}#1\vspace{0.8cm}\end{center} \LARGE}


\begin{document}

\mytitle{Hello world}

Hello world

\centering
$
\pstree[treemode=R]{\Tcircle{b}}{%
  \pstree{\TC*^{a_1}}{%
     \Tr{b_{11}}^{x_1}
     \Tr{b_{12}}_{x_2}
   }
  \pstree{\TC*_{a_2}}{%
     \Tr{b_{21}}^{x_1}
     \Tr{b_{22}}_{x_2}
   }
}
$



\mytitle{Hello world 2}

\psline[linewidth=0.5cm](0,0)(2,0)
\psline[linewidth=0.05cm](2,-1)(6,-1)



\end{document}
