S.A. Kashchenko, "Asymptotical Distributions of Eigenvalues of Periodic and Antiperiodic Boundary Value Problems for Second-Order Differential Equations", Automatic Control and Computer Sciences, 52:7, 797--809 (2018).

S.A. Kashchenko, Asymptotical Distributions of Eigenvalues of Periodic and Antiperiodic Boundary Value Problems for Second-Order Differential Equations, Automatic Control and Computer Sciences, 52:7, 797--809 (2018).