\begin{table}%t12
\caption{Compared relative production rates.\label{tababund}}
%\centerline
{\begin{tabular}{lrrrr}
\hline\hline
Molecule & C/1999 T1 (McN.-H.) & C/2001 A2 (LINEAR) & C/2000 WM$_1$ (LINEAR) & 153P/I.-Z. \\
\hline
$\langle r_{\rm h}\rangle^1$& 1.3		    &	1.1		&	1.2	&	1.0	 \\
\hline
\multicolumn{5}{l}{Abundance relative to water}\\
HCN      & $0.08\pm0.01$\% & $0.14\pm0.01$\%& $0.08\pm0.01$\%  & $0.11\pm0.01$\%              \\
CH$_3$OH & $2.4\pm0.3$\%   & $2.8\pm0.4$\%   & $1.3\pm0.2$\%   & $2.5\pm0.1\times r_{\rm h}^{+0.8}$\% \\
CO       & $15 \pm 5$\%    & $<$$3.7$\%        & $<$$1.4$\%        & $3.8\pm0.6$\%                \\
H$_2$CO  & $0.32\pm0.07$\% & $0.24\pm0.05$\% & $0.37\pm0.05$\% & $0.39\pm0.04$\%              \\
H$_2$CO(p)& $0.16\pm0.04$\% & $0.05\pm0.01$\% &  0.09--0.18\%   & $0.10\pm0.01$\%              \\
H$_2$S   & $0.55\pm0.08$\% & $1.15\pm0.05$\% & $0.13\pm0.02$\% & $0.82\pm0.08$\%              \\
CS       & $0.08\pm0.02$\% & $0.07\pm0.01\times r_{\rm h}^{-5}$\%& $0.05\pm0.01$\% & $0.067\pm0.016\times r_{\rm h}^{-1.0}$\% \\
HNC      & $<$0.007\%      & $0.0066\pm0.0010\times r_{\rm h}^{-2.9}$\% 
                                               & $<$0.003\%      &$0.0053\pm0.0003\times r_{\rm h}^{-2.6}$\% \\
CH$_3$CN & $<$0.052\%      & $0.028\pm0.010$\%& $0.014\pm0.004$\%&  $0.016\pm0.004$\%            \\
\hline
\multicolumn{5}{l}{Abundance relative to HCN}\\
CH$_3$OH & $31\pm5$         & $20\pm2$      & $16\pm2$      & $22\pm6$              \\
CO       & $200\pm80$       & $<$23         & $<$17         & $36\pm8$              \\
H$_2$CO  & $4.0\pm1.0$      & $1.6\pm0.3$   & $4.2\pm0.5$   & $3.6\pm0.3$           \\
H$_2$S   & $6.3\pm1.1$      & $6.9\pm0.7$   & $1.6\pm0.3$   & $7.5\pm0.5$           \\
CS       & $1.1\pm0.2$      & $0.2\pm0.1$   & $0.6\pm0.1$   & $0.55\times r_{\rm h}^{-0.7}$           \\
HNC      & $<$$0.08^2$        & $0.052\times r_{\rm h}^{-3.7}$ & $<$$0.036^3$ & $0.055\times r_{\rm h}^{-2.2}$ \\
CH$_3$CN & $<$0.6           & $0.19\pm0.07$ & $0.18\pm0.04$ & $0.14\pm0.04$         \\
HC$_3$N  &                  & $<$0.05       &               & $<$0.09               \\
OCS      & $<$125           & $<$1.1        &               & $<$2.0                \\
HNCO     &                  & $<$0.23       &               & $0.39\pm0.08$         \\
SO       &                  & $0.8\pm0.2$   &               & $<$$0.5$                \\
HCOOH    &                  & $<$1.3        &               & $<$$0.8$                \\
\hline
\end{tabular}}
\par
\smallskip
$^1$ Mean heliocentric distance (in AU) for the abundances, unless otherwise specified.\\
$^2$ at $r_{\rm h}=1.42$ AU.\\
$^3$ at $r_{\rm h}=1.18$ AU.\\
(p): parent distribution.
\end{table}