\documentclass[10pt,a4paper]{report}
\usepackage[top=3cm, bottom=2.5cm, left=3cm, right=2.5cm] {geometry}
\usepackage {bsymb,b2latex}
\usepackage{fancyhdr,lastpage,color}
\lhead{\rm An Event-B Specification of cx4}
\rhead {\rm Page \thepage~of \pageref{LastPage}}
\lfoot{}\cfoot{}\rfoot{}
\pagestyle{fancy}
%---------------------------------------------------------
\begin{document}
\thispagestyle{empty}
\begin{description}
\BTitle{cx4}{13 Dec 2011}{11:10:14 PM}
\CONTEXT{cx4}
\EXTENDS{cx3}
\CONSTANTS
	\begin{description}
		\Item{ Timeout\_dn }
		\Item{ Timeout\_up }
	\end{description}
\AXIOMS
	\begin{description}
		\nItemX{ Timeout\_dn\_axiom }{ Timeout\_dn \in  \nat_1  }
		\nItemX{ Timeout\_up\_axiom }{ Timeout\_up \in  \nat_1 }
	\end{description}
\END
\end{description}
\end{document}
