  An algorithm for studing the symmetrical properties of the partial
differential equation of the type Lu=0 is proposed. By symmetry of this
equation we mean the operators Q satisfying commutational relations of order p
more than p=1 on the solutions u: [L...[L,Q]...]u=0. It is shown, that within
the framework of the proposed method with p=2 the relativistic D'Alembert and
Maxwell equations are the Galilei symmetrical ones. Analogously, with p=2 the
Galilei symmetrical Schroedinger equation is the relativistic symmetrical one.
In both cases the standard symmetries are realized with p=1.
