Conditional symmetry of the equations of nonlinear mathematical physics

We present a survey of results regarding the investigation of the conditions of the symmetry of nonlinear equations of mathematical and theoretical physics: the wave equation, the Schrödinger, Boussinesq, Korteweg-de Vries, Maxwell, and Dirac equations. We construct families of exact solutions that cannot be obtained by the classical Lie approach.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 11, pp. 1456–1470, November, 1991.