\begin{table}%t6
\caption{\label{tab6}Proposed Identification of the modes in HL Tau 76.}
%\centering
\par
\begin{tabular}{cccc}
\hline\hline
  Periods  (s)  & Period (s) &  Period (s)  & $\ell$  \\
   (XCOV18) &(XCOV13) & Archives   \\
\hline
1390.8 && & 2  \\
 &1347.9&1353.7  & 2  \\
 &&1308.7  & 1  \\
1070.8 && & 2  \\
1067.5 && & 1   \\
1065.0 &1065.0& & 1,2   \\
1061.8 && &1  \\
1060.2 && &2  \\
979.2 && &1,2  \\
976.4 && &1,2\\
974.4 && &1,2\\
971.6 && &1,2\\
933.2 &932.5& &1  \\
930.6 && &1  \\
799.1 && &2 \\
798.3 && &2 \\
796.4 &796.5& &2  \\
794.1 && &2  \\
792.7 && &2  \\
 &781.0& &1  \\
 &&748.5 &2 \\
738.7: &&  &2 \\
  &&689.3 &2 \\
664.2 &&665.0 &2 \\
663.6 && &? \\
662.8 && &? \\
662.3 && &2 \\
661.9 && &? \\
661.4 && &2 \\
660.1 && &?\\
659.5 && &2 \\
 &657.4& &2 \\
 &&628.0 &2 \\
598.6 && &1 \\
597.1 &597.0& &1 \\
596.8 && &1 \\
542.4 && &1 \\
541.8 && &1\\
540.9 &541.0& &1 \\
494.2 &494.2&494.0 &2 \\
493.2 && &2 \\
 &449.8& &1 \\
394.3: & & &1 \\
382.5 &382.5& &2 \\
\hline
\end{tabular}
\end{table}