On a Subharmonic Functional of Some Even Order Elliptic Problems

procedure for finding a subharmonic functional of a solution for the problem Lus nis0 y1.ici Dius0 in the domain E, which is either in a plane or on a line, is presented. The functional obtained is used to derive the maximum principles and uniqueness theorems for some higher order elliptic problems. The procedure proposed is also applicable to nonlinear differential equations