\begin{table}%t1
\caption{Observed lines and rest frequencies used in this work.
\label{tbl-1}}
$$
\begin{array}{lcrrc}
\hline
\noalign{\smallskip}
\mbox{Line} & \mbox{Telescope} & \mbox{Frequency}  & E_l & \mbox{Ref.} \\
& & \mbox{(MHz)} & \mbox{(K)} &  \\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
\mbox{CH$_3$OH(J$_k$=2$_0$--1$_0$)A$^+$~~~~~~} & \mbox{~~IRAM~~} & 
96~741.375 & 2.3 & (1) \\
\mbox{CH$_3$OH(J$_k$=3$_0$--2$_0$)A$^+$} & \mbox{IRAM} & 145~103.200 & 6.7 & (2) \\
\mbox{CH$_3$OH(J$_k$=2$_{-1}$--1$_{-1}$)E} & \mbox{IRAM} & 96~739.362 & 0.0 & (1) \\
\mbox{CH$_3$OH(J$_k$=3$_{-1}$--2$_{-1}$)E} & \mbox{IRAM} & 145~097.450 & 4.6 & (2) \\
\mbox{SO(JN=32--21)} & \mbox{IRAM} & 99~299.890 & 4.5 & (2) \\
\mbox{SO(JN=43--32)} & \mbox{IRAM} & 138~178.670 & 9.2 & (2) \\
\mbox{c-C$_3$H$_2$(J$_{K_{-1}K_{+1}}$=2$_{12}$--1$_{01}$)} & \mbox{IRAM} 
& 85~338.894 & 0.0 & (3) \\
\mbox{c-C$_3$H$_2$(J$_{K_{-1}K_{+1}}$=3$_{12}$--2$_{21}$)} & \mbox{IRAM} 
& 145~089.610 & 6.7 & (3) \\
\mbox{H$_2$CO(J$_{K_{-1}K_{+1}}$=2$_{12}$--1$_{11}$)} & \mbox{IRAM} 
& 140~839.502 & 0.0 & (4) \\
\mbox{H$_2$CO(J$_{K_{-1}K_{+1}}$=2$_{11}$--1$_{10}$)} & \mbox{IRAM} 
& 150~498.334 & 0.3 & (5) \\
\mbox{HC$_3$N(J,F=4,5--3,4)} & \mbox{100m} & 36~392.363 & 2.6 & (4) \\
\mbox{HC$_3$N(J,F=10,11--9,10)} & \mbox{IRAM} & 90~979.002 & 19.7 & (4) \\
\mbox{HCO$^+$(J=1--0)}  & \mbox{FCRAO} & 89~188.523 & 0.0 & (5) \\
\mbox{HCO$^+$(J=3--2)}  & \mbox{IRAM} & 267~557.619 & 12.9 & (5) \\
\mbox{H$^{13}$CO$^+$(J=1--0)}  & \mbox{FCRAO} & 86~754.288 & 0.0 & (6) \\
\mbox{DCO$^+$(J=3--2)}  & \mbox{IRAM} & 216~112.582 & 10.4 & (7) \\
\mbox{C$_2$S(JN=67--56)}  & \mbox{IRAM} & 86~181.391 & 19.2 & (8) \\
\mbox{HCN(JF=12--01)}  & \mbox{FCRAO} & 88~631.847 & 0.0 & (4) \\
\mbox{HCN(JF=34--23)}  & \mbox{IRAM} & 265~886.487 & 12.8 & (4) \\
\mbox{H$^{13}$CN(JF=12--01)}  & \mbox{IRAM} & 86~340.168 & 0.0 & (4) \\
\noalign{\smallskip}
\hline
\end{array}
$$
References: (1) \citet{mul04}; (2) this work; (3) 
C. Gottlieb, priv. comm.; (4) CDMS; (5) JPL; (6) \citet{sch04};
(7) \citet{cas05}; (8) \citet{yam90}.
\end{table}