\begin{table}%t4
\caption{Main physical parameters of our sources found in literature:
dust temperature ($T_{\rm d}$), H$_2$ column and volume 
densities ($N_{\rm H_2}$ and $n_{\rm H_2}$, respectively)
and gas kinetic temperature ($T_{\rm kin}$). The
references are shown between brackets.}
\label{tab_ref}
%\centerline
{
\begin{tabular}{ccccc}
\hline \hline
Source &  $T_{\rm d}$ & $N_{\rm H_2}$ & $n_{\rm H_2}$ &  $T_{\rm kin}$ \\
       &  (K)   &  ($\times 10^{22}$ \cmq ) & ($\times 10^{5}$ \cmc )   &  (K) \\
\hline
05345+3157 & --  &  8.6 (1) & 1.5 (1) &  17.0 (2) \\
05373+2349 & 27(1)   &   5.9 (1) & 2.4 (1) &  21.2 (3) \\
18144+3157 & 29(1)  &  17.7 (1) & 1.8 (1) & 23.6 (3) \\
18511+0146 & 35 (1) &  6.2 (1) & 0.4 (1) & 27.3 (4) \\
18517+0437 & 38 (5) & 68 (6) & 5.4 (6) & 29 (3) \\
19092+0841 & 29 (1) &  12.4 (1) & 1.6 (1) & 40.4 (4) \\
20126+4104 & 62 (5) &   52 (6) & 11.4 (6) & 23.0 (5) \\
20216+4107 & 46 (5) &   18 (6) &  3.1 (6) & 21.0 (5) \\
20343+4129 & 44 (5) &   22 (6) &  3.9 (6) & 18 (5) \\
22172+5549 & 30 (1) &   4.8 (1) & 0.8 (1) & 17.5 (3) \\
\hline  
\end{tabular}
}
\par
(1) Molinari et~al.~(\cite{mol00});
(2) Jijina et~al.~(\cite{jijina}); 
(3) Molinari et~al.~(\cite{mol96});
(4) Brand et~al.~(\cite{brand}); 
(5) Sridharan et~al.~(\cite{sridharan});
(6) Beuther et~al.~(\cite{beuther}).
\end{table}