On non-linear differential equations of the second order. III: The equation \(\ddot y - k(1-y^2) \dot y +y=b \mu k\cos (\mu t + \alpha)\) for large \(k\), and its generalizations. IV: The general equation \(\ddot y + kf(y) \dot y +g(y)=bkp (\varphi),\;\varphi = t + \alpha\)
nonlinear ordinary differential equations of second order
scientific article; zbMATH DE number 3132973