  For a connected regular scheme X, flat and of finite type over Spec(Z), we
construct a reciprocity homomorphism \rho_X: C_X --> \pi_1^\ab(X), which is
surjective and whose kernel is the connected component of the identity. The
(topological) group C_X is explicitly given and built solely out of data
attached to points and curves on X. A similar but weaker statement holds for
smooth varieties over finite fields. Our results are based on earlier work of
G. Wiesend.
