\begin{table}%t1
\caption{\label{T1}Numbers and sources of the spectral lines used for the analysis.}
\par
%\centering
\par
\begin{tabular}{p{0.12\linewidth}ccp{0.35\linewidth}}
\hline \hline \noalign{\smallskip}
            & $\rm (^3P){\it n}s{-}(^3P){\it n}p$ & $\rm (^3P){\it n}p{-}(^3P){\it n}d$ & Reference \\
\hline
 Ne II & 17 &  9 & del Val et~al. (\cite{Val00})	                 \\
                			                   & 10 & 16 & Pel\'aez et~al. (\cite{Pel08})     \\
            Ar II & 15 & 14 & Aparicio et~al. (\cite{Apa98})    \\
			Kr II & 17 &  1 & de Castro et~al. (\cite{Cas01})   \\
				  &  3 &  3 & Djurovi\'c et~al. (\cite{Dju08})  \\
			Xe II & 11 &  2 & Gigosos et~al. (\cite{Gig94})     \\
			      & 15 &  6 & Djurovi\'c et~al. (\cite{Dju06})  \\
\hline
TOTAL & 88 & 52 &     \\
\hline
\end{tabular}
\end{table}