Piotr Berman, Arnab Bhattacharyya, Konstantin Makarychev, Sofya Raskhodnikova, Grigory Yaroslavtsev. Improved Approximation for the Directed Spanner Problem. In Luca Aceto, Monika Henzinger, Jiri Sgall, editors, Automata, Languages and Programming - 38th International Colloquium, ICALP 2011, Zurich, Switzerland, July 4-8, 2011, Proceedings, Part I. Volume 6755 of Lecture Notes in Computer Science, pages 1-12, Springer, 2011. [doi]
Abstract is missing.