Regular Method for Searching of Differential Equations Discrete Symmetries

A new constructive regular method to search discrete symmetries of a set of differential equations is proposed. The method is based on automorphism properties of a basic $1$-forms for initial and transformed equations. In difference with well-known methods of discrete symmetry searching the proposed method does not need in a priori knowledge and as sequence in a preliminary searching of infinitesimal symmetries for studied equations.