\begin{table}%t6
 %\centering
\par
\caption{\label{tab_Z}Metallicities of GRB host galaxies.}
\par
\tiny\begin{tabular}{lccccccccccc}
\hline\hline\noalign{\smallskip}
& {980703}  &  {990712}  & {020405} &  {020903} & {030329} &    {031203} &    {060218} &  060505\tablefootmark{g} &  060505\tablefootmark{h}  &\\
\hline\noalign{\smallskip}
${N_{\rm e}}[{\rm SII}]$\tablefootmark{a}& -- & $20\sim200$ & -- & $20\sim 200$ & $20\sim 200$ & $52.63\pm43.20$ & $120.68\pm32.22$ & -- & --\\
${T_{\rm e}}[{\rm OIII}]$\tablefootmark{b}  & -- & $16434.9\pm425.8$ & -- & $13~517.1\pm335.2$ & $17911.7\pm325.0$ & $12902.2\pm305.2$ & $15113.3\pm335.5 $& -- & --\\
$\rm{12 + \log{(O/H)} }(Te)^{c}$  & -- & $7.812\pm0.15$ & -- & $8.014\pm0.15$ & $7.653\pm0.14$ & $8.142\pm0.07$ &  $7.883\pm0.09$ & -- & --\\
$\rm{12+\log{(O/H)}}$\tablefootmark{d} & $8.28\pm0.14$ & $8.18\pm0.12$\tablefootmark{f}&$ 8.10\pm0.12$ & $8.11\pm0.12$\tablefootmark{f} & $8.06\pm0.10$\tablefootmark{f} & $8.11\pm0.11$\tablefootmark{f}  & $8.16\pm0.14$\tablefootmark{f} & $8.06\pm0.14$\tablefootmark{f} & $7.99\pm0.09$ \\
 $(K99\_l)$ &&&&&&&&&\\
$\rm{12+\log{(O/H)}} $\tablefootmark{d}  & $8.44\pm0.15$ & $8.47\pm0.15$ & $8.53\pm0.15$ & $8.50\pm0.15$ & $8.56\pm0.16$ & $8.51\pm0.15$ &  $8.50\pm0.16$ & $8.57\pm0.15$ & $8.66\pm0.16$\tablefootmark{f} \\
$(K99\_u)$&&&&&&&&&\\
$\log([{\rm NII}]6583$ & -- & --2.36 & -- & --1.47 & --2.12 & --1.23 & --1.45 & --1.36 & --0.52 \\
$/{\rm [OII]}3727)$ &&&&&&&&&\\
$A_{V}^e$ & $0.144\pm0.532$ & $0.551\pm0.025$ & $1.927\pm0.359$ & $0.146\pm0.086$ & $0.244\pm0.046$ & $0.280\pm0.040$ &  $0.000\pm0.018$ & $0.526\pm0.081$ & $1.601\pm0.310$ \\
\noalign{\smallskip}
\hline
\end{tabular}
\tablefoot{\tablefoottext{a}{Electronic density estimated from the
$\rm{[S\ II]}$ flux ratio: $I(6716)/I(6731)$.} 
\tablefoottext{b}{Temperature in~K estimated from the following flux ratios: $\rm{[O\ III]}$
$I(4959+5007)/I(4363)$.} 
\tablefoottext{c}{Metallicity, $12+\log$(O/H), estimated using the effective temperature method.} 
\tablefoottext{d}{Metallicity, $12+\log$(O/H), estimated following \citet{Kobulnicky99}. K99$\_l$ (their Eq.~(8)) is valid for the lower branch; K99$\_u$ (their Eq.~(9)) is valid for the upper branch.}
\tablefoottext{e}{Extinction coefficient, $A_{V}$ (in magnitude) is derived using the standard Balmer ratio of H$\alpha$ and H$\beta$. For GRB~980703 and 020405, ${A}_V$ from the ratio of H$\gamma$ and H$\beta$ is adopted.}
\tablefoottext{f}{Adopted metallicity in this work. The $R_{23}$ degeneracy are broken using the $\rm{[N\ II]}$/H$\alpha$ and
$\rm{[N\ II]}$/$\rm{[O\ II]}$ ratios.}
\tablefoottext{g}{The GRB site.}
\tablefoottext{h}{The entire host galaxy.}}
\end{table}