Cyclic Galois Extensions of Commutative Rings

The structure theory of abelian extensions of commutative
rings is a subjectwhere commutative algebra and algebraic
number theory overlap. This            exposition is aimed at readers
with some background in either of these two   fields. Emphasis
is given to the notion of a normal basis, which allows      one
to view in a well-known conjecture in number theory
(Leopoldt's      conjecture) from a new angle. Methods to
construct certain extensions quite explicitly are also
described at length.