ИСТИНА

The purpose of this report is the demonstration of searching the first integral of motion by the method of normal form. For the object of this demonstration, we chose the Li\'{e}nard equation. We represented the equation as a dynamical system and parameterized it. After a calculation of the normal forms near stationary points, we found parameter values at which the condition of local integrability is satisfied for all stationary points simultaneously. We found two such sets of parameters. For each of them, the global integrability takes place.