\begin{table}%t2
%\centering
\par
\caption{Evolution of the mean pulse height of both PMs (in mV) and values of each change on the high voltages (in V). The added index~$1$ and $2$ indicates the corresponding PM tube. The maximum voltage supported by each PM is 1200~V.}
\label{tabagpm}
\begin{tabular}{ccccc}
\hline\hline
   Date		& $X_{\rm m1}$ &  $X_{\rm m2}$ & Voltage 1 & Voltage 2  \\	\hline		
7-Mar.-96	&	228	&231 		& 889.5	& 967.5	\\
17-Mar.-96	&	247	&245 		& 909.5	& 978.5	\\
21-May-96	&	229.3	&229.5		& 	& 	\\
15-Oct.-96	&	202.5	&211.5		& 	&  	\\
13-Jan.-97	&	187.2	&204.3		& 	&  	\\
15-Mar.-97	&	177.8	&200.5		& 	&   	\\
14-May-97	&	170.2	&197.4		&  	&    	\\
16-Oct.-97	&	159.1	&190.8		&	& 	\\
17-Oct.-97	&	247.8	&236.1		& 959.5	& 1008.5\\
07-Dec.-98	&	221.5	&219.9		&	&	\\
07-Dec.-99	&	214.1	&211.6		&  	&  	\\
12-May-00	&	254.1 	&251.6		& 979.5	& 1028.5\\
16-May-01       &	220.1 	&232.9		&  	& 	\\
15-Apr.-05       &	191.9 	& 201.6		&  	& 	\\
22-Apr.-05       &	 	&		& 1028.5 & 1053.5 \\
18-May-05       &	241.5 	& 250.1		&  &  \\
\hline
\end{tabular}
\end{table}