\begin{table} %t1
\caption{\label{t:dynamo}Parameters of the single ($m=0$) double periodic ($m=1$) cosine 
functions and their superposition ($m=0$/1) fitted to the rotation 
measure variations in the two rings of NGC~4254 (cf. Fig.~\ref{f:rmsect}). 
Amplitude, phase shift, background offset, and the Theil~U coefficient of 
the quality of fit are given. 
}
\small%\centerline
{
\begin{tabular}{lrrrr}
\hline
\hline\noalign{\smallskip}
Dynamo mode  & Ampl.  &  Ph. shift & Offset & Theil U$^a$ \\
\hline
RING 3\\
$m=0$          & 79    & 25 & 23 & 0.58 \\
$m=1$          & 53    & 43 & 41 & 0.83 \\
$m=0$/1        & 79/51 & 34 & 33 & 0.34 \\
\hline
RING 4\\
$m=0$          & 82    & 21 &  2 & 0.57 \\
$m=1$          & 48    & 48 & 17 & 0.94 \\
$m=0$/1        & 71/36 & 33 &  9 & 0.36 \\
\hline \\
\end{tabular}}
\smallskip
$^a$~The Theil~U coefficient is limited to a range from 
zero to one (Theil \cite{theil72}). Zero means a perfect fit.
\label{t:modes}
\end{table}