Simeonov, Pavel S.; Bajnov, Drumi Dimitrov:
Применение метода двусторонних приближений к исследованию периодических систем.
(Russian) [Application of the method of two-sided approximations to the investigation of periodic systems of ordinary differential equations with maxima].Archivum Mathematicum,
vol. 21
(1985),
issue 2,
pp. 65-75