\begin{table}%t2
\caption{Metallicities and observed [CII]/CO(1$-$0) line ratios of nearby galaxies and Galactic star
forming regions. %The derived values for gas density and FUV~strength are also given 
%if available.
\label{tab_ratio}}
\small%\centerline
{
\begin{tabular}{c c c c}
\hline \hline
Object & 12 + log~(O/H) &[CII]/CO(1$-$0)  & References\\
\hline
NGC 1068 & 9.07&6000  &14, 2, 12\\
NGC 1156 & 8.39&10~000 &4\\
NGC 1313 & 8.25&11~740 &14, 7\\
NGC 1569 & 8.08&37~000 &13, 4, 6\\
NGC 4449 & 8.3 &14~000 &8, 6\\
NGC 4736 & 9   & 2500 &14, 2, 12, 10\\
NGC 6946 & 9   &  900 &14, 12\\
   IC 10 & 8.19&14~000 &14, 8, 6\\
  IZw 36 & 7.93&$<$$3000$ &8\\
     M83 & 9.16& 8000 &14, 2, 5\\
     M51 & 9.23& 3500 &14, 9, 5\\
 IC 4622 & 8.09&34~000 &3, 4\\
   Orion & 8.75& 6000 &2, 11\\
     LMC & 8.35& 5600 &1\\
30 Doradus &8.43&69~000&1\\
     SMC & 8.03&13~000 &1\\
\hline
\end{tabular}}
\smallskip
 References. (1) Bolatto et~al. (1999); (2) Crawford et~al. (1985); (3)~\mbox{Heydari-Malayeri} et~al. (1990);
(4) Hunter et~al. (2001); (5) Kramer et~al. (2005); (6) Lord et~al. (1995); (7) Luhmann et~al. (2003); (8)~Mochizuki et~al. (1998);
(9) Nikola et~al. (2001); (10) Petitpas \& Wilson (2003); (11) Simon et~al. (1997); (12) Stacey et~al. (1991); (13)~Talent (1980);
(14) Zaritsky et~al. (1994).
\end{table}