\begin{table}%t2
        \caption{Parameters of  Mercury.\label{paratot}}
      %\centerline
$${\begin{tabular}{lcr}
       \hline
          \hline
          \multicolumn{3}{c}{Mercury}\\
       \multicolumn{3}{c}{Bulk quantities }\\
       \hline
        Mass ($GM_{\odot}$) & = &  $4.9125\times 10^{-10}$ ${(a)}$\\
        Equatorial radius (km)&= & 2439 ${(b)}$ \\
        $J_{2}$      & = & $ (6.0 \pm 2.0) \times 10^{-5}$ ${(b)}$ \\ 
        $C_{22}$   & = & $ (1.0 \pm 0.5) \times 10^{-5}$ ${(b)}$ \\
        \cmrdeux         & = & 0.34 ${(c)}$  \\
               \hline
        \end{tabular}}$$
        \smallskip
        ($a$) JPL; ($b$) Anderson \etal 
      (\cite{Anderson87}); ($c$) Milani \etal \cite{Milani01}.
\end{table}