  Let O be the ring of integers of a number field K. For an O-algebra R which
is torsion free as an O-module we define what we mean by a Lambda_O-ring
structure on R. We can determine whether a finite etale K-algebra E with
Lambda_O-ring structure has an integral model in terms of a Deligne-Ribet
monoid of K. This a commutative monoid whose invertible elements form a ray
class group.
