\begin{table}%t1
\caption{\label{tab1}The GPS sample discussed in this paper.}
%\centerline
{
\small
\begin{tabular}{lccccc}  \hline \hline\noalign{\smallskip}
NED name    & J2000 name & $z^a$ & Observation ID$^b$ & Observation date  &Reference$^c$ \\ \hline
4C+00.02        & 002225+001456 & 0.305 & 0407030101 & 2006-Jun.-26  &(1)\\
COINSJ0111+3906 & 011137+390628 & 0.668 & 0202520101 & 2004-Jan.-09  &(2)\\
PKS0428+20      & 043103+203734 & 0.219 & 0407030201 & 2006-Sep.-02  &(1)\\
PKS0500+019     & 050321+020305 & 0.585 & 0205180601 & 2004-Aug.-18  &(3)\\
B30710+439      & 071338+434917 & 0.518 & 0202520201 & 2004-Mar.-23  &(2)\\
PKS0941$-$080   & 094336$-$081931 & 0.228 & Chandra    &              &(3)\\
B1031+567       & 103507+562847 & 0.450 & 0202520301 & 2004-Oct.-21  &(2)\\
4C+14.41        & 112027+142054 & 0.362 & 0502510201 & 2007-Jun.-13  &(1)\\
4C+32.44        & 132616+315409 & 0.370 & 0502510301 & 2007-Dec.-05  &(1)\\
PKS1345+125     & 134733+121724 & 0.122 & ASCA       &              &(4)\\
4C+62.22        & 140028+621038 & 0.431 & 0202520401 & 2004-Apr.-14  &(2)\\
OQ+208          & 140700+133438 & 0.077 & 0140960101 & 2003-Jan.-31  &(5)\\
PKS1607+26      & 160913+264129 & 0.473 & 0502510401 & 2008-Jan.-17  &(1)\\
                &               &       & 0502510801 & 2008-Jan.-19  &   \\
PKS2008$-$068   & 201114$-$064403 & 0.547 & 0502510501 & 2007-Oct.-12  &(1)\\
PKS2127+04      & 213032+050217 & 0.990 & 0502510601 & 2007-May-17  &($1,6,7$)\\
COINSJ2355+4950 & 235509+495008 & 0.238 & 0202520501 & 2003-Dec.-26  &(2)\\
\hline 
\end{tabular}}
\par
\medskip
$^a$ Data taken from NED. \\
$^b$ XMM-Newton observation ID. \\
$^c$ (1)~This paper; (2)~\citet{vink05}; (3)~\citet{guainazzi06};
(4)~\citet{odea00}; (5)~\citet{guainazzi04}; (6)~\citet{siemiginowska05};
(7)~\citet{siemiginowska08}. 
\end{table}