\begin{table}%t3
\caption{\label{tab3}GRB sample.}
\small%\centerline
 {
\begin{tabular}{l c c c c c c c}
\hline \hline
&&&&&&& \\[-8pt]
GRB& $z^a$ & $E_{\gamma}$($10^{52}$ erg)$^b$ & $T_{90}\rm (s)^c$  &$t_{\rm p}(\rm s)$ & medium type & $\Gamma_0^d$ & References\\
&&&&&&& \\[-8pt]
\hline
060801  &1.131 &0.55 &0.5 &110  &ISM &280  &1, 2, 3 \\
060926  &3.208 &1.0 &8.0 &430  &ISM  & 234& 4, 2, 5\\
080319C &1.95  &6.13 &34 & 360   &ISM &274  &6, 7\\
080413B &1.1   & 1.53  &8.0 & 167 &ISM & 271 &8, 9 \\
\hline
\end{tabular}}
\medskip
References: 1 \citet{Cucchiara06}; 2 \citet{Butler07}; 3 \citet{Sato06}; 4 \citet{Elia06}; 5 \citet{Cummings06}; 6 \citet{Wiersema08}; 7 \citet{Stama}; 8 \citet{Vreeswijk08}; 9
\citet{Barthelmy08};
$^a$ redshift of GRB;
$^b$ isotropic equivalent energy of prompt $\gamma$-ray emission (1$-$$10^4$~keV in the burst frame for bursts with defined redshift to consistent with the catalog in \citealt{Butler07});
$^c$~time duration of GRB;
$^d$ the calculated initial Lorentz factor of fireballs (assuming $n=1~\rm cm^{-3}$ for ISM~case).
\end{table}