\begin{table}%t11
    \hfill
    \caption{Comparison of abundances in \object{BD+30~3639} and \nsix.}
    \label{comparison}
%\centerline
{    \begin{tabular}{l c c l c c c c c}
      \hline
      \hline
      \makebox{\rule[0cm]{0cm}{0.33 cm}Element} & \multicolumn{2}{c}{\bd} &
      & \multicolumn{3}{c}{\nsix}&  Sun$^{1}$ &   O, B Stars$^{2}$ \\
      \cline{2-3} \cline{5-7}
      &\makebox{\rule[0cm]{0cm}{0.33 cm}Present abun.} & AH$^3$&  &
      Present abun. & Mid$^4$& HA$^5$ & &\\
      \hline
      Helium       &          & 0.021    & & 0.118   & 0.11 & 0.130 & 0.098 &      \\
      Carbon (--4)   & 7.3      & 3.60     & & 2.5     & 7.6  & 2.5   & 3.55  &1.74  \\
      Nitrogen (--4) & 1.1      & 1.16     & & 2.3     & 0.84 & 1.2   & 0.93  & 0.65 \\
      Oxygen (--4)   & 4.6      & 3.78     & & 5.5     & 6.4  & 4.7   & 4.90  & 4.17 \\
      Neon (--4)     & 1.9      & $>$0.018 & & 1.9     & 1.6  & 1.0   & 1.20  & 1.23 \\
      Sulfur (--5)   & 0.64     & 0.71     & & 1.3     &      & 0.8   & 1.86  & 1.23 \\
      Chlorine (--7) & 1.4      & 1.44     & & 2.0     &      & 1.6   & 1.86  & 1.86 \\
      Argon (--6)    & 5.2      & $>$0.2   & & 4.2     &      & 3.0   & 3.63  &      \\
      \hline
    \end{tabular}}
  $^{1}$ Solar abundance from \citet{grevesse} and \citet{anders},
  except the oxygen abundance that has been taken from\\ \hspace*{2mm}\citet{allende}.\\
  $^{2}$ O, B star abundances are the average of \citet{gies} and
  \citet{killian}.\\
  $^3$ From \citet{aller}.\\
  $^4$ From \citet{mid}.\\
  $^5$ From \citet{hyung}.
\end{table}