\begin{table}%t5
\caption{References for B3-VLA CSS source flux densities used for the
  spectral analysis.}\label{tab:frequenze}
%\centerline
{
\begin{tabular}{rrrr}
\hline \hline
 Frequency & Reference & Data & \% \\
 MHz      &   & & \\
 (1) & (2) & (3) &  (4)  \\
\hline
151        &  \citet{Hales88}        & 6C Survey  &  98  \\
327	   &  \citet{Rengelink97}    & WENSS      & 100	 \\
408	   &  \citet{Ficarra85}	     & B3 Survey  & 100	 \\
1465	   &  \citet{Condon98}	     & NVSS       & 100	 \\
4850	   &  \citet{Kulkarni90}     & Effelsberg & 	 \\
	   &  \citet{Gregory96}	     & GB6        & 100	 \\
4860	   &  \citet{Fanti01}	     & VLA        & 100	 \\
8460	   &  \citet{Fanti01}	     & VLA        & 100	 \\
10~550	   &  \citet{Gregorini98}    & Effelsberg & 100	 \\
14~940	   &  this article           & VLA        & 67	 \\
32~000	   &  \citet{Mack}           & Effelsberg & 14	 \\
230~000     &  \citet{Klein96}        & IRAM       & 24   \\                
\hline
\end{tabular}}
\medskip
Note. Column~1: observed frequency;
Col.~2: reference;
Col.~3: data;
Col.~4: percentage of the observed B3-VLA CSS~sample. The percentage
refers to the sample of 84~sources (see Sect.~\ref{sec:integrated-spectra}).
\end{table}