Geometric minimality conditions for systems of exponentials in $L_p[-\pi,\pi]$

A proof is given of the stability theorem for minimal systems of exponentials $e(\Lambda)=\{e^{i\lambda x}\}_{\lambda\in\Lambda}$ in $L_p[-\pi,\pi]$, where $\Lambda\subset\mathbb C$ is a discrete subset. Geometric minimality conditions for such systems are obtained.