\begin{table}%T3
\caption{\label{tabfitsum}Overview of best fitting spherical envelope models.}
\scriptsize
%\centering
\par
\begin{tabular}{r r l}
\hline \hline
Isotopologue & Outer abundance\tablefootmark{a}  & Comment \\
\hline\noalign{\smallskip}
o-H$_2$$^{18}$O~& $3 \pm 1 \times 10^{-10}$ & implies o-H$_2$O~$1.7~\pm~0.5\times10^{-7}$\tablefootmark{b}  \\
p-H$_2$$^{18}$O~& $\le 3 \times 10^{-11}$      & implies p-H$_2$O~$1.7\times10^{-8}$\tablefootmark{b}   \\
o-H$_2$O~              & $3 \times 10^{-7}$              & Well constrained by both excited para lines\\
p-H$_2$O~              & $3 \times 10^{-8}$              & $\ge$$10^{-8}$ required for self-absorption \\
\hline
\end{tabular}
\tablefoot{\tablefoottext{a}{The relative abundance of species listed, and not total H$_2$O}\\
\tablefoottext{b}{Assuming $^{16}$O/$^{18}$O~= 550. }}
\vspace*{-4mm}
\end{table}