Graphic methods of investigation of the stability of continuous systems with one nonlinearity of different classes

For continuous stationary system with one nonlinearity from a class characterized by one numerical parameter $d\in[0,\infty]$ simple graphical criteria are proposed whereby the disturbance (in some sense) of the conditions of V. M. Popov's criterion depends on $d$ and which coincide in extreme cases wither with Popov's criterion for systems with an arbitrary nonlinear response $(d=\infty)$ or with a “segment stability” criterion when the nonlinear element is replaced by a set of linear stationary elements with transfer coefficients from the same sector $(d=0)$.