\begin{table}%T6
\par
\caption{Fraction of absorbed sources$^c$.}\label{t6}
%\centerline
{
\begin{tabular}{l|c|c|c}
\hline\hline
$N_{\rm H}$ (cm$^{-2}$) &${<}10^{22}$& $10^{22}{-}10^{23}$& ${>}10^{23}$\\
\hline
$F_{u1}$$^a$ & 52.5/82 & 19/82 & 12.5/82\\
&48.5/82 &20.8/82 &12.7/82\\
$F_{u2}$$^b$ & 18/24 & 3/24 & 1/24\\
&17.9/24 &3.1/24 &3.0/24\\
\hline
\end{tabular}}
\par
\medskip
$^a$ $F_{u1}$: interval from $0.8~\times~10^{-14}$ to $5~\times~10^{-14}$~erg~cm$^{-2}$~s$^{-1}$;
$^b$~$F_{u2}$: interval from $5~\times~10^{-14}$ to $20~\times~10^{-14}$~erg~cm$^{-2}$~s$^{-1}$;
$^c$ The fractions in the two lines for each flux interval were obtained
as described in the text (Sect.~4.1).
\end{table}