\begin{table}%t2
\label{values}
\caption{\label{tab2}Results of the spectral analysis.}
%\centerline
{
\begin{tabular}{cccc}
\hline\hline
GRB~   &$N_{\rm H}$ Gal.$^a$        & $N_{\rm H}$ obs.$^b$   & $\chi^2_{\rm red}$ \\
       &$10^{20}\cmdue$         & $10^{20}\cmdue$    & (d.o.f.)	      \\
\hline
041223 & 10.9 (9.9) [5.6]    &$\rm 16.8^{+5.2}_{-4.2}$ & 0.8 (26)      \\
050124 & 5.2 (2.6) [1.7]     &$\rm 6.2^{+3.9}_{-2.5}$  & 1.3 (35)      \\
050126 & 5.3 (3.2) [2.6]     &$\rm 4.1^{+2.7}_{-2.6}$  & 0.9 (10)      \\
050128 & 4.8 (4.9) [3.8]     &$\rm 12.5^{+1.4}_{-1.3}$ & 1.3 (105)     \\
050215b& 2.1 (2.0) [0.9]     &$<$3.4            & 1.0 (4)       \\
050219a& 8.5 (10.1) [8.1]    &$\rm 30.1^{+6.5}_{-5.9}$ & 1.0 (57) \\     
050219b& 3.8 (3.0) [1.7]     &$\rm 23.8^{+4.0}_{-3.7}$ & 1.0 (98)     \\
050223 & 7.1 (6.6) [4.4]     &$\rm 9.5^{+23.8}_{-7.3}$ & 1.2 (3)      \\
050306 & 3.1 (2.9) [3.5]     &$\rm 46.1^{+35.6}_{-28.8}$& 1.0 (3)      \\
050315 & 4.3 (3.3) [2.5]     &$\rm 14.9^{+3.9}_{-2.2}$ &  1.3 (42)     \\
050318 & 2.8 (1.8) [0.9]     &$\rm 4.2^{+1.9}_{-1.5}$  & 0.8 (39)      \\
050319 & 1.1 (1.2) [0.5]     &$\rm 3.0^{+0.9}_{-0.8}$  & 1.3 (29)      \\
050326 & 4.5 (3.8) [1.8]     &$\rm 18.9^{+7.1}_{-6.0}$ & 1.0 (25)      \\
050401 & 4.8 (4.4) [3.3]     &$\rm 21.1^{+2.2}_{-1.8}$ & 1.0 (297)     \\
050406 & 2.8 (1.7) [1.1]     &$<$6.6            & 1.2 (10)      \\
050408 & 1.7 (1.5) [1.3]     &$\rm 30.7^{+5.5}_{-4.9}$ & 0.9 (45)   \\
050412 & 2.2 (1.7) [1.0]     &$\rm 26.4^{+14.9}_{-12.4}$& 1.4 (11)    \\ 
\hline
\end{tabular}}
\smallskip
$^a$ Column density values are from Dickey \& Lockman (\cite{Dickey1990}). Values between
parentheses are from Kalberla et~al. (\cite{Kalberla2005}) and in square parentheses from
Schlegel et~al. (\cite{Schlegel1998}), using the usual conversion
$N_{\rm H}=5.9\times 10^{21}~E(B-V)\cmdue$. \\ 
$^b$ The values of the column density have been computed at $z=0$ since we do
not have any knowledge of the GRB~redshift for most of them (but see Table~\ref{zz}).
\end{table}