Chris Bourke, Raghunath Tewari, N. V. Vinodchandran. Directed Planar Reachability is in Unambiguous Log-Space. In 22nd Annual IEEE Conference on Computational Complexity (CCC 2007), 13-16 June 2007, San Diego, California, USA. pages 217-221, IEEE Computer Society, 2007. [doi]
Abstract is missing.