ROTATION INVARIANT SECOND ORDER EQUATIONS

I. A. Adamskaya, S. P. Belyaev
Vant. Ser. Metodiki i Programmy Chislennogo Resheniya Zadach Matematicheskoy Fiziki 1983. Вып.1. С. 14-19.

      Second order equations, invariant with respect to space rotation are considered. A matrix structure with second derivatives is investigated. An explicit matrix form is found.