Robert Hieb, R. Kent Dybvig, and Claude W. Anderson, III, Subcontinuations, Lisp and Symbolic Computation 7, 1, 83--110, January 1994 (bibtex).
Continuations have proven to be useful for implementing a variety of control structures, including exception handling facilities and breadth-first searching algorithms. However, traditional continuations are not useful in the presence of concurrency, because the notion of the rest of the computation represented by a continuation does not in general make sense. Traditional continuations can also be difficult to use in nonconcurrent settings, since their global nature is sometimes problematic. This article presents a new type of continuation, called a subcontinuation. Just as a traditional continuation represents the rest of a computation from a given point in the computation, a subcontinuation represents the rest of a subcomputation from a given point in the subcomputation. Subcontinuations may be used to control tree-structured concurrency by allowing nonlocal exits to arbitrary points in a process tree and allowing the capture of a subtree of a computation as a composable continuation for later use. In the absence of concurrency the localized control achievable with subcontinuations makes them more useful than traditional continuations.