  Let G be a complex connected semisimple group, whose simple components have
type A or D. We prove that wonderful G-varieties are classified by means of
combinatorial objects called spherical systems. This is a generalization of a
known result of Luna for groups of type A; thanks to another result of Luna,
this implies also the classification of all spherical G-varieties for the
groups G we are considering. For these G we also prove the smoothness of the
embedding of Demazure.
