The global hypoellipticity of degenerate elliptic-parabolic operators
Kazuo AMANO · Journal of the Mathematical Society of Japan · 1988
As is well-known, there are vast references on (local) hypoellipticity of de- generate elliptic-parabolic operators (cf.[2], [3], [8], [9], [13], [14] and their references).However, one can find only few papers concerned with global hypoellipticity.Oleinik and Radkevich [14] and Fedii [3] proved global hypo- ellipticity of degenerate elliptic-parabolic operators when $S=$ { $x$ : dim Lie$(x)