\begin{table}%t1
%\centering
\par
\caption{Two types of comets as defined by \citet{Gehrz1992} in the view of later papers.\label{tab0}}
\begin{tabular}{lll}
\hline
\hline
Reference & Type I & Type II\\
\hline
\citet{Gehrz1992}:            & no superheat & color temperature excess\\
                             & no or weak silicate feature & strong silicate feature\\
                             & large dust grains & small dust grains\\
%\hline
\citet{Chernova1993}:         & gas-rich & dust-rich\\
& \multicolumn{2}{l}{(as apparent in visual wavelength range)}\\
                             & low polarization? & high polarization\\
%\hline
\citet{Levasseur-Regourd1996}:& low polarization & high polarization\\
%& \multicolumn{2}{l}{ But is this interpretation tenable? }\\
%\hline
This paper:                  & high polarization & high polarization\\
\hline
\end{tabular}
\end{table}