  We examined the complete short cadence sample of Kepler RR Lyrae stars to
further investigate the recently discovered dynamical effects such as period
doubling and additional modes. Here we present the findings on four stars. V450
Lyr may be a non-classical double-mode RR Lyrae star pulsating in the
fundamental mode and the second overtone. In three cases we observe the
interaction of three different modes. Since the period ratios are close to
resonant values, we observe quasi-repetiting patterns in the pulsation cycles
in the stars. These findings support the mode-resonance explanations of the
Blazhko effect.
