\begin{table}%t1
\caption{\label{tab1}Open cluster sample.}
%\centerline
 {\scriptsize
\begin{tabular}{lccccccc}
\hline \hline
ID & [Fe/H] & $N$& [O/Fe]& $\sigma$& [Na/Fe]& $\sigma$& Ref. \\
\hline
Be 17	 &--0.10& 3& 0.13 &0.05 &0.15 & 0.08 &1\\
Be 20	 &-0.45& 2& 0.34 &0.01 &0.27 & 0.10 &2  \\
Be 29	 &--0.54& 2& 0.39 &0.03 &0.43 & 0.01 &2  \\
Be 31	 &--0.56& 1& 0.40 &  --  &0.34 &   --  &2  \\
Cr 261	 &--0.03& 6&--0.03 &0.09 &0.33 & 0.06 &3  \\
M 67	 & 0.03& 6&--0.07 &0.08 &--0.02& 0.07 &4\\
Mel 66	 &--0.38& 2& 0.45 &0.02 &0.24 & 0.03 &5  \\
Mel 71 	 &--0.30& 2&--0.20 &0.01 &0.2  & 0.05 &6 \\
NGC 2112 &--0.10& 2& 0.0  &0.04 &0.1  & 0.02 &6  \\
NGC 2141 &--0.18& 1& 0.16 & --   &0.48 &   --  &2  \\
NGC 2243 &--0.48& 2& 0.18 &0.09 &0.20 & 0.07 &5  \\
NGC 3680 &--0.04& 2& 0.20 &0.05 &0.01 & 0.08 &4\\
NGC 6253 &0.46 & 4&--0.12 &0.06 &0.21 & 0.02 &7 \\
NGC 6791 &0.47 & 4&--0.25 &0.08 &0.13 & 0.21 &7 \\
NGC 6939 &0.00 & 9& 0.04 &0.09 &0.32 & 0.11 &8 \\
NGC 7142 &0.14 & 4& 0.05 &0.03 &0.36 & 0.06 &8 \\
NGC 7789 &-0.04& 9&--0.07 &0.09 &0.28 & 0.07 &10 \\
Praesepe & 0.27& 7&--0.40 &0.20 &--0.04& 0.12 &4 \\
\hline
\end{tabular}}
\par
\smallskip
References:
(1) \cite{friel05};         
(2) \cite{yong05}; 
(3) \cite{carretta05};      
(4) \cite{pace08};  
(5) \cite{gratton};      
(6) \cite{brown};      
(7) \cite{carretta07};      
(8) \cite{jacobson07};        
(9) \cite{jacobson08}; 
(10) \cite{tau05}.        
\end{table}