\begin{table} %T1
      \caption{\label{tab1}The luminosity-redshift bins used for the selection of the sample (for $H_0=70$~km~s$^{-1}$~Mpc$^{-1}$, 
                $\Omega_{\rm m} = 0.3$, $\Omega_{\Lambda}=0.7$).} 
      $$
         \begin{array}{lllllllllll} 
            \hline \hline 
            \noalign{\smallskip} 
 {\rm Bin~no.} & N_{\rm Cl} & L_{\rm X} ({\rm min}) & L_{\rm X} ({\rm max}) & z_{\rm min} & z_{\rm max} & N_{\rm tot} & {\rm vol. cov.} &\rm  sky cov. & {\rm density}^c & {\rm density}^d \\ 
    &     &     &     &     &       &   & {\rm correction}^a & {\rm correction}^b &  &  \\ 
(1) & (2) & (3) & (4) & (5) & (6) & (7) & (8) & (9) & (10) & (11)\\ 
            \noalign{\smallskip} 
            \hline 
            \noalign{\smallskip} 
1  & 4& 0.407 & 0.55 & 0.0555 & 0.06215  & 4  & 0.94 & 0.775 & 5.28(-6) & 4.95(-6) \\ 
2  & 4& 0.55  & 0.78 & 0.0794 & 0.0877   & 4  & 0.86 & 0.775 & 3.33(-6) & 3.12(-6) \\ 
3  & 4& 0.78  & 1.13 & 0.0920 & 0.1037   & 7  & 0.87 & 0.775 & 8.72(-7) & 7.39(-7) \\ 
4  & 4& 1.13  & 1.71 & 0.1077 & 0.12105  & 8  & 0.88 & 0.775 & 3.17(-7) & 2.80(-7) \\ 
5  & 4& 1.71  & 2.88 & 0.1122 & 0.1248   & 4  & 0.94 & 0.775 & 8.87(-8) & 8.39(-8) \\ 
6  & 4& 2.88  & 4.10 & 0.1224 & 0.15215  & 4  & 0.95 & 0.775 & 2.73(-8) & 2.53(-8) \\ 
7  & 4& 4.10  & 5.90 & 0.1337 & 0.16875  & 5  & 0.97 & 0.775 & 1.60(-8) & 1.20(-8) \\ 
8  & 4& 5.90  & 11.9 & 0.1423 & 0.1719   & 4  & 1.00 & 1.0   & 3.17(-9) & 1.33(-9) \\ 
9  & 1& 11.9  & 20   & 0.1623 & 0.19925  & 1  & 1.00 & 1.0   & 3.66(-10)& 1.62(-10) \\ 
% 
            \noalign{\smallskip} 
            \hline 
         \end{array} 
     $$
\begin{list}{}{} 
\item[$N_{\rm Cl}$ is the number of sample clusters per bin.]  
\item[$L_{\rm X}({\rm min})$, $L_{\rm X}({\rm max})$, $z_{\rm min}$, and $z_{\rm max}$ give the luminosity (in  
$10^{44}$ erg s$^{-1}$ {[}0.1$-$2.4~keV{]}) and redshift boundaries of the bins, respectively.]  
\item[$N_{\rm tot}$ is the total number of clusters per bin including the unobserved ones.] 
\item[$^a$ gives the mean volume coverage fraction of the REFLEX survey above the flux limit, for the detection of 30 photons for the bins.]  
\item[$^b$ fraction of sky coverage for an interstellar column  
density $N_{\rm H} \le 6\times 10^{20}$~cm$^{-2}$.] 
\item[$^{c}$ cluster density (Mpc$^{-3}$) determined from the selection 
function derived in Sect.~2.2, where the number in brackets gives 
the exponent of~10.]   
\item[$^{d}$ cluster density (Mpc$^{-3}$) from the alternative method 
  used to determine the selection function.]  
\end{list} 
\end{table}