\begin{table}%t2 
\caption{\label{tab2}Line ratios measured in prototypical regions.}    
%\centering
\par
\begin{tabular}{lcccccc}
\hline
\hline
\noalign{\smallskip}
Source	& ${\rm CH_3OH(2-1)\over SiO(2-1)}$ & ${\rm CH_3OH(3-2)\over SiO(3-2)}$& ${\rm HNCO(4-3)\over SiO(2-1)}$& ${\rm SiO(2-1)\over CN(2-1)}$& ${\rm CN(2-1)\over HCN(1-0)}$ & References\\ 
\noalign{\smallskip}
\hline
\noalign{\smallskip}
NGC 1068-CND		&2.3$^*$~(1.8)  & 2.1$^*$~(1.7) &  1.2$^*$~(1.2) & 0.9 & 0.25 & 1, 2 \\
\noalign{\smallskip}
L1157-B1		& 2$^*$~(1.7) & 1.9$^*$~(1.7) & -- & 3$^*$~(7.5) & 0.11$^*$~(0.04) & 3, 4  \\
L1157-B2		& 2.3$^*$~(2.1) & 2.9$^*$~(2.7) & -- & $>$7$^*$~($>$12) & $<$0.04$^*$~($<$0.03) & 3, 4  \\
\noalign{\smallskip}
IC~342-Ndisk 		&-- & 4.5$^*$~(3.6) & -- & -- & --& 5, 6   \\
IC~342-N arm 	& 5 & -- & 3.5 & -- & -- & 7, 8  \\ 
\hline
\end{tabular}
\tablefoot {We list line ratios derived in the CND of NGC~1068 (NGC~1068-CND), the B1 and B2 bullets of the young stellar object L1157, as well as the nuclear disk 
and Northern spiral arm of the nearby galaxy IC~342 (IC~342-Ndisk and IC~342-N arm, respectively). Line ratios are given in $T_{\rm mb}$ units; these are corrected by source coupling factors for single-dish observations. Uncorrected ratios are identified by an asterisk; corrected ratios (in $T_{\rm b}$-{\it source} units) are given in parentheses when necessary.}
\par
\tablebib {(1)~ U04; (2)~this work; (3)~Nisini et~al.~(\cite{Nis07}); (4)~P\'erez-Guti\'errez~(\cite{Per99}); (5)~H\"uttemeister et~al.~(\cite{Hue97}); (6)~Garc\'{\i}a-Burillo \& Mart\'{\i}n-Pintado~(\cite{GarMP01}); (7)~Meier \& Turner~(\cite{Mei05}); (8)~Usero et~al.~(\cite{Use06}).}
\par
\end{table}