\begin{table}%t5
      \caption{\label{tab:xc}Physical conditions estimated from line ratios$^{{a}}$ and line intensities.}
         \small
	%\centerline
{
         \begin{tabular}{lcccc}
            \hline\hline
            \noalign{\smallskip}
            Molecule/ratio & $\nh2$ & $T_{\rm K}$ & $N/\Delta\upsilon^{{b}}$ & $\tau^{{b}}$ \\
                           & [$\3cm$] & [K] & [$\ndv$] & \\
            \noalign{\smallskip}
            \hline
            \noalign{\smallskip}
            HCN & $10^4{-}10^7$ & $>$$20$ & $10^{13.2}{-}10^{15.2}$ & $10^{-3.0}<\tau_{1-0}<10^{2.4}$ \\
                &             &       &                       & $10^{0.2}<\tau_{3-2}<10^{2.8}$ \\
                &             &       &                       & $10^{0.2}<\tau_{4-3}<10^{2.8}$ \\
            \noalign{\smallskip}
                         HNC & $10^4{-}10^7$ & $10{-}90$ & $10^{12.8}{-}10^{15.0}$ & $10^{-1.0}<\tau_{1-0}<10^{2.6}$ \\
                &             &       &                         & $1<\tau_{3-2}<10^{2.8}$ \\
                &             &       &                         & $10^{-0.6}<\tau_{4-3}<10^{2.4}$ \\
            \noalign{\smallskip}
             CN & $10^{5.2}{-}10^7$ & $10{-}20$ & $10^{14}{-}10^{15.2}$ & $10^{-2.0}<\tau_{1_{3/2}-0_{1/2}}<10^{2.4}$ \\
                &             &       &                          & $1<\tau_{2_{5/2}-1_{3/2}}<10^{2.8}$ \\
                &             &       &                          & $10^{-0.4}<\tau_{3_{5/2}-2_{5/2}}<10^{1.4}$ \\
            \noalign{\smallskip}
                       \hcop $\frac{4-3}{3-2}$ & $10^{5.9}{-}10^7$ & $>$$30$ & $10^{11.9}{-}10^{12.2}$ & $10^{-4.0}<\tau_{3-2}<10^{-1.2}$ \\
                &             &       &                         & $10^{-2.2}<\tau_{4-3}<10^{-1.2}$ \\
     \noalign{\smallskip}	    	    
            \hline
         \end{tabular}}
\smallskip
${^a}$ Results from the single-phase model with a source size $\theta_{\rm S}=1.5''$.\\
${^b}$ In order to get the actual column density and optical depth, the values reported here must be multiplied by a pertinent line width, i.e. thermal plus turbulent width ({\it FWHM}) of the lines. According to Schinnerer \etal~(\cite{Schinnerer2000}), the velocity dispersion at the nuclear region of NGC~1068 is about~23~\kms. 
\end{table}