% Bernd Berg Oct 12 2017.
 \documentclass{ws-book9x6}  
\begin{document} 

\begin{figure}[th] % From EMscript/figures_plt/minkowski_space_sol.
\vskip -60pt
\centerline{\hbox{\psfig{figure=figures/2DtwinIRS,width=13cm} }}
IRS: Minkowski space in which observer~B is at rest and observer~A 
moves with speed $4/5$ in negative $x'$ direction. % \end{figure}
\bigskip \bigskip

% \begin{figure}[th] % See subfolder minkowski2Dtwin.
\centerline{\hbox{\psfig{figure=figures/2DtwinFRS,width=13cm} }}
FRS: Minkowski space in which observer~B is at rest and observer~A 
moves with speed $4/5$ in positive $x''$ direction. \end{figure}

\end{document}
