\begin{table}%t7
%\centering
\par
\caption{Radio power density.\label{tab_powerdensity}}
\begin{tabular}{lll}
\hline
\hline
Survey & $U_{1.4~{\rm{GHz}}}$  & References \\
 & {\scriptsize 10$^{18}$ W~Hz$^{-1}$~Mpc$^{-3}$ }  & \\
\hline
CIG  & $4.44 \pm 0.52$  & This paper \\
IRAS-2Jy & $15.60 \pm 0.25$  & Yun et~al. (\cite{yun01}) \\
UGC/NVSS-SF & $17.06 \pm 0.35$  &  Condon et~al. (\cite{condon02})  \\
UGC/NVSS-AGN & $41.88 \pm 3.47$  & Condon et~al. (\cite{condon02})  \\
2dFGRS & $74.76 \pm 3.59$ & Sadler et~al. (\cite{sadler02}) \\
\hline
\end{tabular}
\end{table}