Hypoelliptic second order differential equations

Linear Partial Differential Operators

1963 • 2,444 citations

The Structure of Lie Groups.

1967 • 676 citations

Non‐coercive boundary value problems

1965 • 431 citations

Zufallige Bewegungen (Zur Theorie der Brownschen Bewegung)

1934 • 316 citations

Degenerate elliptic-parabolic equations of second order

1967 • 223 citations

Boundaries of Complex Manifolds

1965 • 172 citations

Solvability of a first order linear partial differential equation

1963 • 152 citations

The fundamental solution of a degenerate partial differential equation of parabolic type

1951 • 57 citations