They developed a complete theory for the solvability of boundary-value problems for uniformly parabolic and uniformly elliptic quasilinear second-order equations and of the smoothness of generalized solutions.
Sila ay binuo ng isang kumpletong teorya para sa kasugiran ng boundary-halaga para sa mga problema uniformly paparabola at uniformly tambilugin quasilinear second-order ng mga equation at ang kinis ng pangkalahatan solusyon.