Shapovalov, Yuriy     Theoretical bases of asymptotic stability assessment of linear parametric circuits according to frequency method [Текст] / Yuriy Shapovalov, Bohdan Mandziy // Computational problems of electrical engineeringVol. 1. Vol. 1. N. 1 ; Lviv Polytechnic Nat. Univ. ; ed.-in-chief Yuriy Bobalo - Lviv : Lviv Polytechnic Nat. Univ. , 2011. — P. 83-88.