Stability criteria for parametric system consisting of two coupled circuits with external conductor link
A more general Lyapunov function has been proposed in the form of instantaneous energy stored in reactances that allowed us to obtain several new stability criteria for a parametric system consisting of two coupled circuits with external conductor coupling.
N. D. Biryuk, Yu. B. Nechaev, and S. Yu. Alekhin, “A Problem of Stability of Parametrical System of Two Coupled Circuits with External Conductive Connection,” Izv. Vyssh. Uchebn. Zaved., Radioelektron. 51(8), 32 (2008) [Radioelectron. Commun. Syst. 51(8), 426 (2008)].
B. P. Demidovich, Lectures on the Mathematical Stability Theory (Nauka, Moscow, 1967) [in Russian].