Ya. V. Delyukova
Department of Mathematics
Ussuriisk State University
692512 Ussuriisk, Russia
We consider the problems of a reduction and solution for non-linear determining systems of partial differential equations. We have these systems by searching discrete transformation groups, nonlocal symmetries of ordinary differential equations, and also nonclassical symmetries of non-linear equations of mathematical physics. We proove that we can reduce the dimension of the system if the class of equation D has a priori symmetries.