\begin{table}%tA.1
\caption{\label{thtop}p-\HTHOP\ column density upper limits.}
\small%\centerline
 {
\begin{tabular}{lcccccccc}
\hline\hline
Source &  $T_{\rm rms}$ & $T_{\rm R}$ & $\Delta {v}^{(a)}$ & $\eta_{\rm b}$  & $N_1^{(b)}$ &
$T_{\rm ex_1}$ & $N_2^{(c)}$ & $T_{\rm ex_2}$   \\
name   & (K) & (K) & (\kms ) &  & (\cmsq ) & (K) & (10$^{15}$ \cmsq ) & (K) \\
\hline
IRAM~04191 & 0.054 & $<$0.16 & 0.35 & 0.65  & $<$3.5 & 7.0 & $<$1.1 & 4.1 \\
L~1521F    & 0.042 & $<$0.13 & 0.31 & 0.65  &  $<$0.90 & 6.1 & $<$0.85 & 4.1 \\
L~1544     & 0.025 & $<$0.08 & 0.33 & 0.65 &  $<$0.55 & 6.1 & $<$0.63 & 3.9 \\
L~183      & 0.031 & $<$0.09 & 0.23 & 0.6 & $<$0.53 & 5.9 & $<$0.50 & 3.9 \\
Oph~D    & 0.083 & $<$0.25 & 0.24 & 0.6 & $<$0.30 & 6.0 & $<$1.1 & 4.3 \\
L~429      & 0.043 & $<$0.13 & 0.40 & 0.6 & $<$1.5 & 5.5 & $<$1.1 & 4.1 \\
L~694-2   & 0.046 & $<$0.14 & 0.28 & 0.6 & $<$0.90 & 5.9 & $<$0.80 & 4.1 \\
\hline
\end{tabular}}
\medskip
$^{{a}}$ Assumed value, derived from previous \NTHP (1--0) observations (see text);
$^{{b}}$~column density value obtained using $n$(\MOLH) and $T_{\rm kin}$ from Table~\ref{tcolumn};
$^{{c}}$~column density value assuming $n$(\MOLH)~= 10$^5$~\percc\ and $T_{\rm kin}$~=~10~K.
\end{table}