  In 1995, Meinardus & Berg presented a reformulation of the Collatz Conjecture
in terms of a functional equation in a single complex variable over the open
unit disk. This paper generalizes that method to deal with not only a large
class of Collatz-type maps defined on the integers, but further generalizations
thereof to Collatz-type maps on the rings of integers on an arbitrary algebraic
number field.
