[1]
KolomiyetsV.G., SamoilenkoA.M. and SamoilenkoV.G. 1998. The Third Bogolyubov Readings. International Scientific Conference “Asymptotic and Qualitative Methods in the Theory of Nonlinear Oscillations”. Ukrains’kyi Matematychnyi Zhurnal. 50, 4 (Apr. 1998), 599.