David A. Schmidt. Closed and Logical Relations for Over- and Under-Approximation of Powersets. In Roberto Giacobazzi, editor, Static Analysis, 11th International Symposium, SAS 2004, Verona, Italy, August 26-28, 2004, Proceedings. Volume 3148 of Lecture Notes in Computer Science, pages 22-37, Springer, 2004. [doi]