\begin{table}%T2
\caption{\label{tab2}Observing parameters.}
\small%\centerline
{
\begin{tabular}{l l c c c l}
\hline\hline
 Transition   &\hskip1mm Frequency & Ref.   &\hskip-1mm {\it HPBW}      &\hskip-1mm Res. &\hskip0.5mm $T_{\rm sys}$ \\
              & \hskip3mm (GHz)    &        &\hskip-1mm (\arcsec) &\hskip-1mm  (km~s$^{-1}$) &\hskip1mm  (K)      \\
\hline
HCO$^{+}$(1$-$0) &\hskip1.5mm  89.188518 &  2  &\hskip-1mm 27       &\hskip-1mm 0.13  &\hskip1.5mm   200  \\
H$^{13}$CO$^{+}$(1$-$0) &\hskip1.5mm  86.754330 & 1 &\hskip-1mm 27 &\hskip-1mm  0.13  &\hskip1.5mm   200  \\
$^{13}$CO(2$-$1) & 220.398686 &   2 &\hskip-1mm 11      &\hskip-1mm  0.11  &  1200  \\
C$^{18}$O(2$-$1) & 219.560328 &   2 &\hskip-1mm 11      &\hskip-1mm  0.11  &  1340  \\
CS(2$-$1)        &\hskip1.5mm 97.980953  &   1 &\hskip-1mm 25      &\hskip-1mm  0.12  &\hskip1.5mm   260  \\
CS(3$-$2)        & 146.969049 &   2 &\hskip-1mm 17      &\hskip-1mm  0.16  &\hskip1.5mm   690  \\
CS(5$-$4)        & 244.935560 &   1 &\hskip-1mm 10      &\hskip-1mm  0.10  &  1830  \\
C$^{34}$S(2$-$1) &\hskip1.5mm 96.412961  &  1 &\hskip-1mm 25      &\hskip-1mm  0.12  &\hskip1.5mm   290  \\
C$^{34}$S(3$-$2) & 144.617147 &   2 &\hskip-1mm 17      &\hskip-1mm  0.16  &\hskip1.5mm   560  \\
C$^{34}$S(5$-$4) & 241.016113 &   1 &\hskip-1mm 10      &\hskip-1mm  0.10  &  2100  \\
\hline
\end{tabular}}
\smallskip
The references for the line frequencies are 1 - Lovas (2003); 
2 - Brand et~al. (2001).
\end{table}