\begin{table}%t2
      \caption{\label{tab:beams}Beamsizes \& efficiencies. }
   \small%\centerline
{
         \begin{tabular}{lcccc}
            \hline\hline
            \noalign{\smallskip}
            Transition & $\nu$ & {\it HPBW}$^{a}$ & $\eta_{\rm mb}$$^{a}$ & Telescope$^{a}$\\
	               & [GHz] &    [$''$]       &                             &   \\
            \noalign{\smallskip}
            \hline
            \noalign{\smallskip}
            HCN~1--0 &  88.632 & 44 ~28& 0.65 ~0.77& OSO  ~IRAM\\
            HNC~1--0 &  90.663 & 55 ~27& 0.74 ~0.77& SEST ~IRAM\\
            CN~1--0  & 113.491 & 45 ~22& 0.71 ~0.74& SEST ~IRAM\\
            CO~1--0  & 115.271 & 44 ~21& 0.70 ~0.74& SEST ~IRAM\\
            CN~2--1  & 226.875 & 23 ~11& 0.51 ~0.53& SEST ~IRAM\\
            CO~2--1  & 230.538 & 20 ~11& 0.66 ~0.52& JCMT ~IRAM\\
            HCN~3--2 & 265.886 & 18 ~9 & 0.60 ~0.45& JCMT ~IRAM\\
            HNC~3--2 & 271.981 & 18 ~9 & 0.60 ~0.44& JCMT ~IRAM\\            
            \noalign{\smallskip}
            \hline
         \end{tabular}}
    \smallskip
\begin{list}{}{}
\item[$^{{a}}$] The columns are divided in two sub-columns 
(\emph{left}: OSO, SEST, JCMT, and \emph{right} IRAM) indicating the 
telescope used to obtain the corresponding parameter. 
The IRAM~30~m telescope was used to observe NGC~3079. The other sources 
were observed with the OSO~20~m, SEST and JCMT telescopes.
\end{list} 
  \end{table}