\begin{table}%t3
%%\centering
\par
\caption{Enhancement factors $q_{{\rm Model}~x/ {\rm Model}~y} = f_{i,{\rm Model}~x}/f_{i,{\rm Model}~y}$ for different line transitions.}%\label{tratio}
%\centerline
{
\begin{tabular}{cccc} \hline\hline
\noalign{\smallskip}
Ratio & H$^{13}$CO$^+$ $3{-}2$ & H$^{13}$CO$^+$ $4{-}3$ & H$^{13}$CO$^+$ 
$8{-}7$ \\ \hline
$q_{1/0}$ & 1 & 1 & 4 \\
$q_{2/0}$ & 1 & 1 & 2 \\
$q_{3/0}$ & 1 & 2 & 10 \\
$q_{4/0}$ & 2 & 4 & 43 \\
$q_{5/0}$ & 2 & 4 & 36 \\
$q_{6/0}$ & 2 & 4 & 38 \\
$q_{2/1}$ & 1 & 1 & 1 \\
$q_{3/1}$ & 1 & 2 & 3 \\
$q_{4/1}$ & 2 & 4 & 11 \\
$q_{5/1}$ & 2 & 4 & 9 \\
$q_{6/1}$ & 2 & 4 & 10 \\ \hline\hline
\noalign{\smallskip}
Ratio & HCS$^+$ $6{-}5$ & HCS$^+$ $8{-}7$ & HCS$^+$ $10{-}9$ \\ \hline
$q_{1/0}$ & 1 & 3 & 8 \\
$q_{2/0}$ & 1 & 1 & 2 \\
$q_{3/0}$ & 3 & 7 & 19 \\
$q_{4/0}$ & 17 & 61 & 169 \\
$q_{5/0}$ & 14 & 51 & 141 \\
$q_{6/0}$ & 13 & 49 & 138 \\
$q_{2/1}$ & 1 & 0.5 & 0.2 \\
$q_{3/1}$ & 2 & 2 & 2 \\
$q_{4/1}$ & 12 & 21 & 20 \\
$q_{5/1}$ & 10 & 18 & 17 \\
$q_{6/1}$ & 10 & 17 & 16 \\ \hline
\end{tabular}}
\label{tratio2}
\medskip
The values represent the ratios of the integrated line fluxes $f = \int 
T_{{\rm mb}} {\rm d}V$. The Models are described in Table~\ref{tmod} in 
Sect.~\ref{presults}.
\end{table}