\begin{table}%T2
\caption{Column densities.}\label{t2}
%\centerline
{
\begin{tabular}{lccc}
\hline\hline
Source & $N$(\hocp) & $N$(\hcop) & $N$(OH) \\ 
 & $10^{10}\pcc$& $10^{12}\pcc$ & $10^{13}\pcc$ \\ 
\hline
B0355+508 & 9.01(1.07) & 6.51(0.02) & 14.87(0.67) \\
B0415+379 & 10.9(0.90) & 12.8(0.40)$^2$ &  42.50(0.10)\\
B0528+134 & ${<}7.7^1$ & 2.28(0.02) &  4.72(0.31)\\
B1730-130 & ${<} 5.7^1$ & 1.25(0.02) &  1.34(0.08)\\
B2200+420 & 3.7(1.3) & 2.58(0.03) &  5.73(0.21)\\
\hline
\end{tabular}}
\par
\medskip
$^1$ Limits are $2\sigma$. \\
$^2$ Entry is $59\pm 2$ $N$(H$^{13}$CO\p).
\end{table}