\begin{table}%t3
\caption{\label{t:deltaY}Summary of differences in $Y$ between first and second-generation stars.  }
\par
%\centerline
{\small
\begin{tabular}{l cccc c cccc}
\hline\hline
Sample & $\Delta {Y_{\rm PI}}(V-K)$  & $\Delta {Y_{\rm PE}}(V-K)$
       & $\Delta {Y_{\rm PI}}$[Fe/H]  & $\Delta {Y_{\rm PE}}$[Fe/H] 
       &
       & $\Delta {Y_{\rm PI}}(V-K)$  & $\Delta {Y_{\rm PE}}(V-K)$
       & $\Delta{Y_{\rm PI}}$[Fe/H]  & $\Delta {Y_{\rm PE}}$[Fe/H] \\
\hline
\multicolumn{1}{c}{} &\multicolumn{4}{c}{Case $a$} & &\multicolumn{4}{c}{Case $b$} \\ 
 \cline{2-5} \cline{7-10} 
 all	      &   ...   & 0.049 &  ...	& 0.046 & &  ...   & 0.077  &  ... & 0.11 \\ 
 all(+corr.)$^1$     &   ...   & 0.064 &  ...	&   ...  & &  ...   & 0.100  & ...   &  ...  \\ 
NGC~2808      & 0.047 & 0.057 & 0.109   & 0.146 & &  0.075 & 0.089  & 0.14  & 0.19 \\ 
NGC~2808(+corr.)$^1$ & 0.063 & 0.072 & ...	&  ...   & &  0.098 & 0.113  & ...&  ... \\ 
\hline
\end{tabular}}
\tablefoot{$^1$ With correction for the CO bands.}\vspace*{-2mm}
\end{table}