\begin{table}%t2
\caption{Previous pulsation frequency determinations for HD~104237. The first column indicates the year of observation, the second column the frequency; the corresponding period is shown in Col.~3;
Col.~4 indicates spectroscopic or photometric oscillation amplitudes; the Col.~5  indicates the reference: [1] Donati et~al. (\cite{donati}), the 0.65~km~s$^{-1}$ amplitude in this table is calculated as half of the 1.3~km~s$^{-1}$ peak-to-peak amplitude stated in the paper; [2]~Kurtz \& M\"uller (\cite{kumu2001}).}\label{prev}
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\par
\begin{tabular}{llllc}
\hline\hline
Year    &  Frequency & Period &Amplitude &Reference\\
            &  (d$^{-1}$)  &  (min)    &                   &         \\
\hline
1993    & $f_1$ = 37.3  & 38.6     &  0.65 km~s$^{-1}$ & [1]\\
1995    & $f_1$ = 39.6  & 36.4     &  0.65 km~s$^{-1}$& [1]\\
1998    & $f_1$ = 33.29 & 43.3    &  11.2 $\pm$ 0.5 mmag& [2]\\
             & $f_2$ = 36.61 & 39.3    &  3.4 $\pm$ 0.5 mmag& [2]\\
\hline
\end{tabular}
\end{table}