  A superstring of a set of strings correspond to a string which contains all
the other strings as substrings. The problem of finding the Shortest Linear
Superstring is a well-know and well-studied problem in stringology. We present
here a variant of this problem, the Shortest Circular Superstring problem where
the sought superstring is a circular string. We show a strong link between
these two problems and prove that the Shortest Circular Superstring problem is
NP-complete. Moreover, we propose a new conjecture on the approximation ratio
of the Shortest Circular Superstring problem.
