\begin{table}%t4
\par
\caption{\label{table:4}Mixing ratios in comet 8P/Tuttle.} 
%\centerline
 {\small\begin{tabular}{c c c c }       % centered columns (4 columns) 
\hline\hline                 % inserts double horizontal lines 
Molecules & This work & Bonev et~al. (2008) & Boehnhardt et~al. (2008) \\ 
\hline 
HCN            & 0.07~$\pm$~0.02 &  0.07~$\pm$~0.02 &   \\ % inserting body of the table 
C$_{2}$H$_{2}$ & 0.05~$\pm$~0.02 &  $<$0.04       &   \\ % inserting body of the table 
CH$_{4}$       & 0.6~$\pm$~0.4   &  0.37~$\pm$~0.07 & 0.36~$\pm$~0.09/0.37~$\pm$~0.08$^{1}$ \\ % inserting body of the table 
C$_{2}$H$_{6}$ & 0.23~$\pm$~0.04 &  0.24~$\pm$~0.03 & 0.30~$\pm$~0.09/0.28~$\pm$~0.06$^{1}$  \\ % inserting body of the table 
CH$_{3}$OH     & 3.3~$\pm$~0.4   &  2.18~$\pm$~0.07 & 3.36~$\pm$~0.40/3.24~$\pm$~0.32$^{2}$ \\ % inserting body of the table 
\hline 
\end{tabular} }
\par
\smallskip
$^1$ Measurements of January 26/27.\\
$^2$ Measurements of January 27/28.
\end{table}