Symmetry and Integrability of Equations of Mathematical Physics − 2013 Irina Yehorchenko (Institute of Mathematics of NAS of Ukraine, Kyiv, Ukraine) Classification of partial differential equations with respect to reductions Abstract: We consider different approaches to classification of PDEs with respect to possible reductions to equations with smaller number of independent variables. As not all reductions are Lie symmetry reductions, the approaches of group classification in general are not applicable. Examples considered are the nonlinear wave equation and the Schrödinger equation.