\begin{table}%t3
\caption{\label{stat}Values of the statistical quantities for 3 targeted MSPs.
} 
%\centerline
{\begin{tabular}{rrrrrr}
\hline\hline 
PSR & $x_0 [\rm Hz^{-2}$] & $std [\rm Hz^{-2}]$ &  $x_0 / std $ & $ \theta^{\rm u.l.} $ / $std[]$ & $ \theta^{\rm u.l.} [\rm Hz^{-2}]$  \\
\hline 
 0024-7204J & $1.00 \times 10^{-36}$ & $5.75 \times 10^{-37}$ & 1.74 & 8.8 & $8.83 \times 10^{-36}$ \\
0218+4232 & $9.50 \times 10^{-37}$ & $7.09 \times 10^{-37}$ & 1.34 & 8.0 & $7.60 \times 10^{-36}$ \\
1939+2134 & $9.22 \times 10^{-37}$ & $5.62 \times 10^{-37}$ & 1.64 & 8.6 & $7.93 \times 10^{-36}$ \\
\hline
\end{tabular}}
\medskip
\par
$x_0$ is the value of the bin 0 of the averaged spectrum; $std$ is
the standard deviation of the noisy bins of the same spectrum;
$\theta^{u.l.}$ is the upper limit on the parameter $\theta$ to
estimate. 
\end{table}