Hiroshi Nagamochi On 2-Approximation to the Vertex-Connectivity in Graphs. 12-16 http://search.ieice.org/bin/summary.php?id=e88-d_1_12&category=D&year=2005&lang=E&abst= 2005 88-D IEICE Transactions 1 db/journals/ieicet/ieicet88d.html#Nagamochi05