\begin{table}%t1
\caption{The epochs, frequencies and arrays of the VLBI~observations described in this paper. In Col.~4 we indicated the polarization  mode of the observation. In Col.~5 references for previously published data are given.}\label{tab:data}
%\centering
\par
\begin{tabular}{crccc}
\hline \hline
Epoch & \multicolumn{1}{c}{Frequency} & Instrument & Pol. & Reference \\
\hline
1992.44 & 22 GHz & EVN (8 stations) & LL & this paper \\
1994.17 & 22 GHz & VLBA (8 stations) + VLA + EVN (4 stations) & LL & this paper \\
1995.27 & 15 GHz & VLBA (2~cm Survey) & RR & \cite{2cmsurvey} \\
1995.96 & 15 GHz & VLBA (2~cm Survey) & LL & \cite{2cmsurvey} \\
1996.73 & 43 GHz & VLBA+EB & full & this paper \\
1996.73 & 22 GHz & VLBA+EB & full & this paper \\
1996.73 & 15 GHz & VLBA+EB & full & this paper \\
1996.82 & 5 GHz & EVN (8 stations) & LL & this paper \\
1996.83 & 8 GHz & EVN (8 stations) & RR & this paper \\
1997.19 & 15 GHz & VLBA (2~cm Survey) & LL & this paper \\
1998.14 & 1.6 GHz & EVN (9 stations) & LL & this paper \\
1999.01 & 15 GHz & VLBA (2~cm Survey) & LL & \cite{2cmsurvey} \\
2001.17 & 15 GHz & VLBA (2~cm Survey) & LL & \cite{2cmsurvey} \\
2001.98 & 15 GHz & VLBA (2~cm Survey) & LL & \cite{kovalev} \\
2003.04 & 22 GHz & VLBA & full & \cite{uwe_thesis} \\
2003.04 & 15 GHz & VLBA & full & \cite{uwe_thesis} \\
2003.16 & 15 GHz & VLBA (MOJAVE) & full & \citet{mlister,kovalev} \\ 
\hline
\end{tabular}
\end{table}