\begin{table}%T5
\caption{The close environments of the RQQs$^a$.}
\label{environment}%\centerline
 {\small
\begin{tabular}{@{}llll@{}}
\hline\hline
%\noalign{\smallskip}
Name & $z$ & $N_{\rm r}$ & $N_{\rm r}$ \\
 & & (50~kpc) & (100~kpc) \\
%\noalign{\smallskip}
\hline
%\noalign{\smallskip}
HS 0010+3611   & 0.530 & 0 & 0\\
1E 0112+3256   & 0.764 & 0 & 1\\
PB 6708        & 0.868 & 1 & 1\\
KUV 03086-0447 & 0.755 & 0 & 0\\
US 3828        & 0.515 & 1 & 1\\
MS 08287+6614  & 0.610 & 0 & 1\\
TON 392        & 0.654 & 0 & 1\\
US 971         & 0.703 & 0 & 0\\
HE 0955-0009   & 0.597 & 0 & 0\\
HE 1100-1109   & 0.994 & 0 & 3\\
CSO 769        & 0.850 & 0 & 0\\
HS 1623+7313   & 0.621 & 0 & 0\\
HS 2138+1313   & 0.810 & 2 & 3\\
LBQS 2249-0154 & 0.832 & 0 & 2\\
ZC 2351+010B   & 0.810 & 0 & 1\\
%\noalign{\smallskip}
\hline
\end{tabular}}
\medskip
$^a$ Column (1) gives the name of the object; (2) the redshift of the object; (3) the number of 
companions within 50~kpc radius; (4) the number of companions within 100~kpc radius.
\end{table}