\begin{table}%T2
      \caption{Historic pulsar periods, corrected for binary
                 doppler shift. The errors given for the corrected periods
                 are taken from the errors given for the observed periods
                 (except for the value marked$^{{a}}$).}
         \label{Tab4HistPeriods}
        \small %\centerline
{
         \begin{tabular}{l l l c l l}
         \hline \hline
                Date     & Obs. period & Corr. period                & Orb. phase & Instrument              & Reference \\
                {[MJD]}  & [s]        & [s]                          &            &                  & \\
         \hline
                43~755.2  & 38.218     & 38.2393 (40)                 &  0.34 & \emph{HEAO A-2}              & \citet{1979ApJ...233L.121W} \\
                44~110.2  & 38.019     & 38.0424 (90)                 &  0.32 & \emph{Einstein MPC}          & \citet{1980MNRAS.193P..49P} \\
                45~535    & 37.885     & 37.8671 (90)$^{{a}}$ &  0.69 & \emph{Tenma GSPC}            & \citet{1984PASJ...36..667N} \\
                47~237.5  & 37.747     & 37.7289 (10)                 &  0.63 & \emph{Ginga LAC}             & \citet{1990PASJ...42..785K} \\
                47~258.5  & 37.725     & 37.7058 (10)                 &  0.64 & \emph{Ginga LAC}             & \citet{1990PASJ...42..785K} \\
                47~589.5  & 37.713     & 37.7355 (30)                 &  0.32 & \emph{Ginga LAC}             & \citet{1990PASJ...42..785K} \\
                47~977    & 37.853     & 37.8652 (200)                &  0.41 & \emph{SIGMA}                 & \citet{1991ApJ...366L..23M} \\
                48~305    & 37.7897    & 37.7621 (3)                  &  0.81 & \emph{ART-P}                 & \citet{1991IAUC.5342....2S} \\
                48~490    & 37.6726    & 37.6707 (15)                 &  0.51 & \emph{SIGMA}                 & \citet{1991IAUC.5342....2S} \\
                50~683.954&            & 37.347411 (6)$^{{b}}$&       & \emph{RXTE}                  & \citet{Baykal2000}          \\
                50~708.5  & 37.39      & 37.3649 (100)                &  0.85 & \emph{ASCA}                  & \citet{Audley2006}          \\
                51~950.84 & 37.329     & 37.3019 (200)                &  0.75 & \emph{Chandra HETGS/ACIS-S}  & \citet{2002ApJ...573..789C} \\
         \hline
         \end{tabular}}
         \smallskip
        $^{{a}}$ Averaged over 5 days, resulting in an increased error;
        $^{{b}}$ published value already corrected for binary motion,
                               $\dot{P}=+(4.56\pm 0.13)\times 10^{-9}$~s~s$^{-1}$. 
   \end{table}