1. On periodical solutions of differential equations involving a time lag;Krasovsky, N. N.;Dokl. Akad. Nauk SSSR (N.S.),1957
2. Almost periodic oscillations in nonlinear systems with retardation.;Šimanov, S. N.;Dokl. Akad. Nauk SSSR,1959
3. On the vibration theory of quasilinear systems with lag;Šimanov, S. N.;J. Appl. Math. Mech.,1959
4. Linear functional-differential equations with constant coefficients;Hale, Jack K.;Contributions to Differential Equations,1963