\begin{table}%t5
\caption{\label{table:5}Mixing ratios of comet 8P/Tuttle, other HFCs and LPCs.} 
%\centerline
 {
\begin{tabular}{c c c c c c c }       % centered columns (4 columns) 
\hline\hline                 % inserts double horizontal lines 
Comets & HCN & C$_{2}$H$_{2}$ & CH$_{4}$ & C$_{2}$H$_{6}$ & CH$_{3}$OH & Remarks \\ 
\hline 
8P/Tuttle        & 0.07~$\pm$~0.02 & 0.05~$\pm$~0.02 & 0.6~$\pm$~0.4   & 0.23~$\pm$~0.04 & 3.3~$\pm$~0.4 & HFC, This work \\ 
153P/Ikeya-Zhang & 0.18~$\pm$~0.05$^{1}$ & 0.18~$\pm$~0.05$^{1}$ & 0.51~$\pm$~0.06$^{2}$ & 0.62~$\pm$~0.18$^{3}$ & 2.5~$\pm$~0.5$^{4}$ & HFC \\ 
1P/Halley        & $\sim$0.08--0.16$^{5,6,7}$     & $\sim$0.3$^{8}$     & $<$1$^{8}$          & $\sim$0.4$^{8}$     & 1.7~$\pm$~0.4$^{9}$ & HFC \\ 
C/1996 B2 & 0.18~$\pm$~0.04$^{10}$  & 0.16~$\pm$~0.08$^{11}$  & 0.79~$\pm$~0.08$^{2,12}$  & 0.62~$\pm$~0.07$^{9,13}$ & 1.7~$\pm$~0.4$^{14}$ & LPC \\ 
C/1995 O1 & 0.27~$\pm$~0.04$^{11}$ & 0.31~$\pm$~0.1$^{11}$  & 1.45~$\pm$~0.16$^{2,15}$ & 0.56~$\pm$~0.049$^{16}$  & 2.4~$\pm$~0.3$^{17}$ & LPC \\ 
C/1999 H1 & 0.29~$\pm$~0.02$^{18}$ & 0.27~$\pm$~0.03$^{18}$ & 1.45~$\pm$~0.18$^{2}$    & 0.67~$\pm$~0.07$^{18}$   & 2.1~$\pm$~0.5$^{18}$ & LPC \\ 
C/2001 A2 & 0.6~$\pm$~0.01$^{19}$  & 0.5~$\pm$~0.1$^{19}$   & 1.2~$\pm$~0.2$^{20}$     & 0.5~$\pm$~0.1$^{19}$     & 3.9~$\pm$~0.4$^{19}$ & LPC \\ 
C/1999 S4 & 0.10~$\pm$~0.03$^{21}$ & $<$0.12$^{21}$       & 0.18~$\pm$~0.06$^{2,21}$ & $<$0.12$^{21}$         & $<$0.15$^{21}$ & LPC \\ 
C/2004 Q2 & 0.16~$\pm$~0.01$^{22}$  & 0.054~$\pm$~0.004$^{22}$ & 1.0~$\pm$~0.1$^{22}$  & 0.42~$\pm$~0.01$^{22}$   & 2.7~$\pm$~0.1$^{22}$ & LPC \\ 
\hline 
\end{tabular} }
\par
\smallskip
 HFC : Halley Family Comet,  LPC : Long Period Comet. \\
$^1$ \citet{mageesauer02a}, $^{2}$ \citet{gibb03}, $^3$ \citet{dellorusso02a}, 
$^4$ \citet{disanti02},
$^5$ \citet{bockeleemorvan87}, $^6$ \citet{schloerb}, $^7$ \citet{despois86}, 
$^8$ \citet{eberhardt99},
$^9$ \citet{eberhardt94}, $^{10}$ \citet{mageesauer02b}, $^{11}$ \citet{mageesauer01}, 
$^{12}$ \citet{mumma96}, $^{13}$ \citet{dellorusso02b}, $^{14}$ \citet{bivera},
$^{15}$ \citet{weaver}, $^{16}$ \citet{dellorusso01}, $^{17}$ \citet{biverb}, 
$^{18}$ \citet{mumma01a},
$^{19}$ \citet{mageesauer08}, $^{20}$ \citet{gibb07}, $^{21}$ 
\citet{mumma01b}, $^{22}$ \citet{kobayashi09} (For CH$_{3}$OH, 
the same $g$-factor is used as Bonev's and Boehnhardt's. Mixing ratio listed here is higher by a factor of two 
than the reported value in their original paper see, \citealt{kobayashi09}.)
\par
\end{table}