\begin{table}%t2
%\centering
\par
\caption{\label{refs}References to the $UBVRI$ observations of HD~50138 shown in  Fig.~\ref{ubvri}.}
\small \begin{tabular}{ll}
    \hline     \hline
 Julian dates & Reference \\
 $[$2~400~000+] &  \\
    \hline
39~916--40~464 & Haupt \& Schroll (\cite{Haupt}) \\
40~556--41~224 & Penston (\cite{Penston}) \\
43~350--44~200 & Alvarez \& Schuster (\cite{Alvarez}) \\
44~589--44~596 & de Winter et~al. (\cite{deWinter}) \\
44~934--45~809 & Kilkenny et~al. (\cite{Kilkenny}) \\
46~392--48~331 & Halbedel (\cite{Halbedel}) \\
48~699--48~707 & de Winter et~al. (\cite{deWinter}) \\
    \hline
\end{tabular}
\end{table}