Riquier problem for a nonlinear equation resolved with respect to the iterated Levi Laplacian
Solutions are found for the nonlinear equation Δ L 2 U(x) = f(U(x)) (here, Δ L is an infinite-dimensional Laplacian) which is solved with respect to the iterated infinite-dimensional Laplacian. The Riquier problems are stated for an equation of this sort.
English version (Springer): Ukrainian Mathematical Journal 50 (1998), no. 11, pp 1796-1800.
Citation Example: Feller M. N. Riquier problem for a nonlinear equation resolved with respect to the iterated Levi Laplacian // Ukr. Mat. Zh. - 1998. - 50, № 11. - pp. 1574–1577.