\begin{table}%t1
\caption{\label{tab:table1}Pairwise peculiar velocity dispersion~(${\rm km~s^{-1})}$.}
%\centering
\par
\begin{tabular}{l c c l}
\hline\hline
Survey&$\sigma_{12}$&$\Delta\sigma_{12}$& {Reference}\\
\hline
CfA1 & 340 & 40 & Davis \& Peebles (\cite{davis83})\\
IRAS 1.2Jy & 317 & 40 & Fisher et al. (1994) \\
CfA2+SSRS & 540 & 180 & Marzke et al. (\cite{marzke})\\
LCRS &  452 & 60 & Lin et al. (1995)  \\
PPRS  &  345 & 95 & Guzzo et al. (\cite{guzzo}) \\
TNRS &  326 & 67 &  Small et al. (1999)  \\
Duhram/UKST GRS  & 416 & 36 & Ratcliffe et al. (\cite{ratcliffe})  \\
CfA2+SSRS & 295 & 99 &  Marzke et al. (\cite{marzke}) \\
LCRS  &  363   & 44 & Landy et al. (\cite{landy1}) \\
LCRS   &  570   & 80 & Jing et al. (1998)  \\
LCRS   &  510   & 70 & Jing \& Borner (2001) \\
2dF   &  331   & 19 &  Landy (\cite{landy2}) \\
SDSS   &  357   & 17 &  Landy (\cite{landy2}) \\
\hline
\end{tabular}
\end{table}