Vikraman Arvind, Jacobo Torán. Sparse Sets, Approximable Sets, and Parallel Queries to NP. In Christoph Meinel, Sophie Tison, editors, STACS 99, 16th Annual Symposium on Theoretical Aspects of Computer Science, Trier, Germany, March 4-6, 1999, Proceedings. Volume 1563 of Lecture Notes in Computer Science, pages 281-290, Springer, 1999. [doi]
Abstract is missing.