$C^{\infty }$ approximations of convex, subharmonic, and plurisubharmonic functions

Greene, R. E.; Wu, H.

Annales scientifiques de l'École Normale Supérieure, Volume 12 (1979) p. 47-84

Embedding of open riemannian manifolds by harmonic functions

Greene, Robert E.; Wu, H.

Annales de l'Institut Fourier, Volume 25 (1975) p. 215-235