$\begin{figure} \resizebox{\hsize}{!}{\includegraphics{2251_1.ps}} \end{figure}$

The light curves for the source 2251+158 (The same as Fig. 1 for the source 2251+158).

$\begin{figure} \resizebox{\hsize}{!}{\includegraphics{2251_2.ps}} \end{figure}$

Autocorrelation (ACF) and cross correlation (DCF) results for 2251+158 (The same as Fig. 2 for 2251+158).

$\begin{figure} \resizebox{\hsize}{!}{\includegraphics{2251_3.ps}} \end{figure}$

Modelling the light curve with exponential flares for 2251+158 (37 GHz) (The same as Fig. 3 for 2251+158 37 GHz).

$\begin{figure} \resizebox{\hsize}{!}{\includegraphics{2251_4.ps}} \end{figure}$

Modelling the light curve with eponential flares for 2251+158 (22 GHz) (The same as Fig. 3 for 2251+158 22 GHz).

$\begin{figure} \resizebox{\hsize}{!}{\includegraphics{2251_5.ps}} \end{figure}$

Optical flux level vs. phase $\Phi$ and flux of the model radio outbursts for 2251+158 (37 GHz) (The same as Fig. 4 for 2251+158 37 GHz).

$\begin{figure} \resizebox{\hsize}{!}{\includegraphics{2251_6.ps}} \end{figure}$

Optical flux level vs. phase $\Phi$ and flux of the model radio outbursts for 2251+158 (22 GHz) (The same as Fig. 4 for 2251+158 22 GHz).