\begin{table}%t4
%\centering
\par
\caption{Reference for the optical constant of amorphous materials used in the radiative
transfer modelling.}\label{tab:dustopac}
\small \begin{tabular}{ll}
\hline \hline
Solid species & Reference\\
\hline
\noalign{\smallskip}
TiO$_2$[s]     & Ribarsky et~al. (\cite{Ribarsky85})\\
SiO$_2$[s]     & Henning et~al. (\cite{Henning1997})\\
SiO[s]         & Philipp in Palik (1985)\\
Mg$_2$SiO$_4$[s] & J\"ager et~al. (2003)\\
MgSiO$_3$[s]   & Dorschner et~al. (\cite{Dorschner1995}) \\
MgO[s]         & Hofmeister et~al. (\cite{Hofmeister2003})\\
Al$_2$O$_3$[s] & Begemann et~al. (\cite{Begemann1997})\\
Fe[s]          & Ordal et~al. (\cite{Ordal1985})\\
FeO[s]         & Henning et~al. (\cite{Henning1995})\\
FeS[s]         & Begemann et~al. (\cite{Begemann1994})\\
Fe$_2$O$_3$    & \url{ http://www.astro.uni-jena.de/Laboratory/}\\
               & \url{OCDB/index.html}\\ 
CaTiO$_3$[s]   & Posch et~al. (\cite{Posch2003})\\
\hline
\end{tabular}    
\end{table}