\begin{table}%t12
%%\centering

\par
\caption{\label{Molecular abundance in a sample of four low-mass protostars}Molecular abundance in a sample of four low-mass protostars (Bottinelli et~al. \cite{Bottinelli07}).}
\begin{tabular}{lrrrrl}
\hline\hline\noalign{\smallskip}
Molecule         & IRAS16293-2422      & NGC1333-IRAS4A     & NGC1333-IRAS4B    & NGC1333-IRAS2A      & Ref.\\
\hline\noalign{\smallskip}
H$_2$CO          & $1.0\times10^{-7}$   & $2.0\times10^{-8}$  & $3.0\times10^{-6}$ & $2.0\times10^{-7}$   & 1,2,3 \\
CH$_3$OH         & $1.0\times10^{-7}$   & $<$$1.0\times10^{-8}$ & $7.0\times10^{-7}$ & $3.0\times10^{-7}$   & 4 \\
HCOOCH$_3$-A     & $1.7\times10^{-7}$   & $3.4\times10^{-8}$  &  $1.1\times10^{-6}$ & $<$$6.7\times10^{-7}$ & 5,2,6 \\
HCOOH            & $6.2\times10^{-8}$   & $4.6\times10^{-9}$ & $<$$1.0\times10^{-6}$ & $<$$1.2\times10^{-7}$ & 5,2,6 \\
CH$_3$OCH$_3$    & $2.4\times10^{-7}$   & $<$$2.8\times10^{-8}$ & $<$$1.2\times10^{-6}$ & $3.0\times10^{-8}$  & 5,2,6,7 \\
CH$_3$CN         & $1.0\times10^{-8}$   & $1.6\times10^{-9}$  &  $9.5\times10^{-8}$ & $8.7\times10^{-9}$  & 5,2,6 \\
C$_2$H$_5$CN     & $1.2\times10^{-8}$   & $<$$1.2\times10^{-9}$ & $<$$7.5\times10^{-7}$ & $<$$1.0\times10^{-7}$ & 5,2,6 \\
\hline
\end{tabular}
\tablebib{(1) Ceccarelli et~al. (\cite{Ceccarelli00}); (2) Bottinelli et~al. (\cite{Bottinelli04}); (3) Maret et~al. (\cite{Maret04});
(4)~Maret et~al. (\cite{Maret05}); (5)~Cazaux et~al. (\cite{Cazaux});
(6)~Bottinelli et~al. (\cite{Bottinelli07}); (7)~J{\o}rgensen et~al. (\cite{Jorgensen}).}
\end{table}