The second method of Lyapunov is used to validate Aizerman\´s conjecture for the class of third-order nonlinear control systems described by the following differential equation: 

 In this case, the stability of the nonlinear system may be inferred by considering an associated linear system in which the nonlinear function 

 is replaced by 

 . If the linear system is asymptotically stable for 

 , then the nonlinear system will be asymptotically stable in-the-large for any 

 for which 

 The Lyapunov function used to prove this result is determined in a straightforward manner by considering the physical behavior of the system at the extreme points of the allowable range of 

 .