\begin{table}%t1
\caption{Main properties of the emission lines detected in the optical 
spectrum of Swift J1656.3$-$3302. Line fluxes are reported with and 
without correction for the intervening Galactic extinction (see text).
Equivalent Widths (EWs) are expressed in the observer's frame.
Uncertainties are at 1-$\sigma$ confidence level.}\label{tab1}
\small
%\centerline
{\begin{tabular}{lcccc}
\hline\hline
\noalign{\smallskip}
\multicolumn{1}{c}{Line} & \multicolumn{2}{c}{Flux (10$^{-15}$~erg~cm$^{-2}$~s$^{-1}$)} & {\it EW} & {\it FWHM} \\
\cline{2-3}
\noalign{\smallskip}
 & observed & extinction- & (\AA) & (km~s$^{-1}$) \\
 & & corrected & & \\
%\noalign{\smallskip}
\hline
%\noalign{\smallskip}
Lyman-$\alpha$$^*$ & $2.8 \pm0.3 $  & $ 39\pm4  $  & $263\pm26$ & $\sim$9900  \\
Si {\sc iv}        & $0.41\pm0.12$ &  $4.4\pm1.3$ &  $ 30\pm10$ & $\sim$5000  \\
C {\sc iv}         & $1.19\pm0.12$ &  $7.2\pm0.7$ &  $ 80\pm8 $ & $\sim$6600  \\
He {\sc ii}$^*$    & $0.66\pm0.13$ &  $2.3\pm0.5$ &  $ 43\pm9 $ & $\sim$12~000 \\
C {\sc iii}]$^*$   & $1.1 \pm0.1 $  & $5.1\pm0.5$ &  $ 65\pm7 $ & $\sim$9300  \\
\hline
\end{tabular}}
\smallskip
$^*$ Possibly blended with a fainter emission line (see text).
\end{table}