Madhav V. Marathe, Harry B. Hunt III, S. S. Ravi. The Complexity of Approximating PSPACE-Complete Problems for Hierarchical Specifications (Extended Abstract). In Andrzej Lingas, Rolf G. Karlsson, Svante Carlsson, editors, Automata, Languages and Programming, 20nd International Colloquium, ICALP93, Lund, Sweden, July 5-9, 1993, Proceedings. Volume 700 of Lecture Notes in Computer Science, pages 76-87, Springer, 1993.
Abstract is missing.