\begin{table}%t2
\caption{Fractional abundances of H$_2$O, CH$_3$OH, and Si/SiO assumed for the icy mantles and the grain cores.}\label{tab0bis}
\small%\centerline
{  
\begin{tabular}{ccc}      
\hline\hline       
 Species & \multicolumn{2}{c}{Abundances [$\chi$]} \\
 & Mantles & Cores \\ 
\hline         \noalign{\smallskip}           
   H$_2$O & $7.25 \times 10^{-5}$$^{a}$ & $\ldots$ \\
   CH$_3$OH & ${\sim}10^{-6}$$^{b}$ & $\ldots$ \\
   Si/SiO & ${\sim}10^{-8}$$^{b}$ & ${\sim}3.6\times 10^{-5}$$^{c}$ \\
\hline                  
\end{tabular}}
\smallskip
$^{a}$~From \citet{whi91}.~$^{b}$ From \citet{jim05}.\\
$^{c}$ From \citet{and89} and \citet{snow96}.
\end{table}