\begin{table}%t4
\caption{\label{tab:Contour_nH}Constraints on the intrinsic column density
derived from iso-HR contours in the $\Gamma$ versus $N_{\rm H}$
parameter space. No constraint can be derived for 4C+00.02.}
%\centerline
{\small
\begin{tabular}{lccc} 
\hline \hline
Source         & $N_{\rm H,max}$ & $F_{2-10}$$^a$ & $\log (L_{2-10})$ \\ 
&  (10$^{21}$~cm$^{-2}$)  & \\ \hline
PKS0428+20   & $<$6.9 & [0.3, 0.6] & 43.1 \\
4C+14.41     & $<$1.6 & [0.2, 0.5] & 43.1 \\
PKS2008$-$068 & $<$4.8 & [0.2, 0.5] & 43.8 \\
\hline
\end{tabular}}
\par
\medskip
$^a$~Ranges  in units of
10$^{-13}$~erg~s$^{-1}$~cm$^{-2}$
corresponding to the $N_{\rm H}$ range as in this table, and to the
photon index in the range: [0.63,2.62] (more details in text). 
\end{table}