P. P. Avrashkov
Oryol State Technical University,
Naugorskoe shosse 29, Oryol
V. F. Zaitsev
Russian State Pedagogical University,
nab. r. Moyki 48, Saint-Petersburg
We consider the 3-rd order ordinary differential equations:
y'''=F(x,y).
We proved that the class of ODEs has only 25 special subclasses of the
nonlinear equations. These equations admit a Lie point symmetry and
have quadratic (on y'') first integrals.