\begin{table}%T4
\caption{VLBA observations: source and calibrators list.\label{log_vlba}}
\par
%\centerline
 {
\begin{tabular}{lcclc}
\hline\hline
Source & \multicolumn{2}{c}{Core absolute position} & Calibrator & Separation \\
 & (RA, $^{\rm h~m~s}$) & (Dec, $^{\circ}~'~''$) & & ($^{\circ}$) \\
\hline
0222+36 & 02 25 27.327 &37 10 27.746 & J0226+3421 &  2.8 \\
0258+35 & 03 01 42.329 &35 12 20.298 & J0310+3814 &  3.8 \\
0648+27 & 06 52 02.517 &27 27 39.405 & J0646+3041 &  3.5 \\
1037+30 & 10 40 29.945 &29 57 57.791 & J1037+2834 &  1.5 \\
1855+37 & 18 57 37.52  &38 00 33.7   & J1912+3740 &  3.7 \\
\hline 
\end{tabular}}
\smallskip
Note -- Incomplete coordinates for 1855+37 are due to the lack of a detection
in the VLBA and VLA 22~GHz data. Therefore, the absolute position reported here
is taken from the VLA data at 8.4~GHz.
\end{table}