\begin{table}%t4
\setlength\tabcolsep{11pt}
  \caption{\label{dispempi}Results of the comparison between the oxygen abundance given by several empirical calibrations and the oxygen abundance derived here following the direct (\Te) method.}
%\centerline
{
\begin{tabular}{l@{\hspace{8pt}}  c@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}} c@{\hspace{8pt}}c@{\hspace{8pt}} c@{\hspace{8pt}}  c 
c@{\hspace{8pt}}  c@{\hspace{8pt}} c@{\hspace{8pt}} c c@{\hspace{8pt}} c@{\hspace{8pt}} } %  c@{\hspace{8pt}}}
   \noalign{\smallskip}
  \hline\hline
Parameter   & \multicolumn{6}{c@{\hspace{4pt}}}{$R_{23}$} & & \multicolumn{3}{c@{\hspace{4pt}}}{N$_2$} & & 
\multicolumn{2}{c@{\hspace{4pt}}}{O$_3$N$_2$} \\
  \cline{2-7} \cline{9-11} \cline{13-14}
         \noalign{\smallskip}
calibration\tablefootmark{a} &  P01   & PT05  &  N06  & M91  & KD02 & KK04  & & D02  &  PP04 &   N06 & & PP04  &  N06    \\ % &  Izotov06 \\
\tableline
\noalign{\smallskip}    
Average\tablefootmark{b} &  0.07  & 0.08 &  0.14  & 0.15 & 0.28 & 0.27  & & 0.14    & 0.12    &  0.18 & & 0.12 & 0.21    \\ % & 0.03\\
 $\sigma$\tablefootmark{c}   &  0.05  & 0.07 &  0.12  & 0.11 & 0.18 & 0.13  & & 0.10    & 0.10    &  0.14 & & 0.10 & 0.16   \\ % & 0.03\\
 Notes\tablefootmark{d}      & B/A (1)& B/A  &   (2)  & S.H. & S.H. & S.H.  & & S.H. (3)& B/A (4) &  S.L.(5)  & & B/A (6) & S.L.      \\ 
\hline
  \end{tabular}}
  \tablefoot{\tablefoottext{a}{The names of the calibrations are the same as in Table~\ref{abempirica2}.}
\tablefoottext{b}{Average value (in absolute values) of the difference between the abundance given by empirical calibrations 
and that obtained using the direct method. The names of the calibrations are the same as in Table~\ref{abempirica2}.} 
\tablefoottext{c}{Dispersion (in absolute values) of the difference between the abundance given by empirical calibrations and that obtained using the direct method.}
\tablefoottext{d}{We indicate if the empirical calibration gives results both below and above the direct value (B/A), if they are systematically higher than the direct value (S.H.) or if they are systematically lower than the direct value (S.L.). Some additional notes are: 
  (1) Higher deviation in the low branch. (2) This calibration provides lower oxygen abundances in low-metallicity regions and higher oxygen abundances in high-metallicity regions. (3)~Systematically higher only for $\abox>8.2$. (4) Higher deviation for  $\abox<8.0$. Considering $\abox>8.0$, we get average = 0.08 and $\sigma=0.06$. (5) Higher deviation at lower oxygen abundances. (6) Higher deviation for $\abox<8.0$. Assuming $\abox>8.0$, average = 0.09 and $\sigma=0.06$. }}\vspace*{1mm}
\end{table}