  A Seifert manifold is a 3-dimensional manifold with a circle action. It is a
circle bundle (with singularities) over a 2-dimensional orbifold.
  In this note, we discuss a generalized Seifert manifolds. By definition, they
have bundle-like structures whose fibers are infra- homogeneous spaces; that
is, the fibers are flat manifolds, almost flat manifolds, etc.
  We prove existence, uniqueness, rigidity theorems. Many interesting
properties and applications are presented.
