\begin{table}%t4
%\centering
\par
\caption{\label{tab:sizeindex}Size distribution index of the Kuiper belt populations.}
\begin{tabular}{cccc}
\hline\hline
\noalign{\smallskip}
CKB &	RES	& SDO & Reference\\
\hline
$4.3\pm 0.2$		&  $5.1\pm 0.1$	& $2.8\pm 0.1$	& this paper\\
$4.8^{+0.5}_{-0.6}$	&		&		& \cite{Gladman-et-al-1998}\\
$4.0\pm 0.5$		&		&		& \cite{Jewitt-et-al-1998}\\
$3.7\pm 0.2$		&		&		& \cite{Luu-Jewitt-1998}\\
$3.6\pm 0.1$		&		&		& \cite{Chiang-Brown-1999}\\
$4.4\pm 0.3$		&		&		& \cite{Gladman-et-al-2001}\\
$4.0^{+0.6}_{-0.5}$     &		&		& \cite{Trujillo-et-al-2001a}\\
$4.05 \pm 0.2$		&		&		& \cite{Bernstein-et-al-2004}\\
$3.97\pm 0.15$		&$3.30\pm 0.37$ &$3.02\pm 0.32$	& \cite{Donnison-2006}\\
\hline
\end{tabular}
\end{table}