Joseph Cheriyan John H. Reif Directed <i>s-t</i> Bumberings, Rubber Bands, and Testing Digraph <i>k</i>-Vertex Connectivity. 335-344 1992 conf/soda/1992 SODA http://dl.acm.org/citation.cfm?id=139404.139473 db/conf/soda/soda92.html#CheriyanR92