\begin{table}%tA.1
\caption{\label{features}Summary of features useful for spectral classification between O4 and B9 in the 6300$-$9000~\AA\ range.}
%\centering
\par
\begin{tabular}{lllll}
\hline \hline \noalign{\smallskip}
Feature & From & To & Maximum& Comments\\ 
     &  &            &             & \\     
\hline
Paschen lines   &  O4 & B9 & $>$B9 & Number of lines seen depends on temperature and luminosity\\
& & & & Shape of lines correlates with luminosity\\ 
\ion{He}{i} 6678, 7065~\AA\ & O4 & $\sim$B7~V, B9~I & B2 & \\
\ion{He}{i} 8847, 8777, 8583~\AA\ &O8--9 & B3~V, B6~I& B2 & strength depends on luminosity \\
\ion{He}{ii} 6683~\AA\ & O4 & O7~V, O9~I & O4 & blended with \ion{He}{i} 6678~\AA \\
\ion{He}{ii} 8283~\AA & O4 & O9~I--V & O4 & inside telluric band\\
\ion{C}{iii} 8500~\AA & $\sim$O6 & B0.5 & O9 & lower limit not well determined\\
\ion{C}{ii} 6578, 6582~\AA & B0.7 & B6~III, B8~I & B3 & rarely seen in dwarfs\\
\ion{C}{ii} 7231, 7236~\AA & O9.7~I & B2~I & B1 & emission features only in luminous SGs\\
&&&& inside telluric band\\
\ion{O}{i} 8446~\AA & B2~V B1.5~I & B9 & $>$B9 & strong dependence on luminosity\\
\ion{O}{i} 7774~\AA & B3~V B1~I & B9 & $>$B9 & strong dependence on luminosity\\
\ion{Si}{ii} 6347, 6371~\AA & B2~I & B9 & B8 & tabulated by \citet{lennon93} in SGs\\
\ion{Si}{iv} 6668, 6701~\AA & $-$ & O9 & ? & emission lines in SGs; lower limit not determined\\
\ion{N}{i} 8680--86, 8703--18~\AA & B3~I--II & B9~I-II &$>$B9  & not seen in III--V\\
\ion{N}{ii} 6482, 6610~\AA & B1~I & B3~I & B2  & only strong in Ia SGs\\
\ion{Ne}{i} 6402~\AA & B1~I & B9~I & B4--5  & tabulated by \citet{lennon93} in SGs\\
\hline
\end{tabular}
\end{table}