Stefan Dobrev Paola Flocchini Rastislav Kralovic Nicola Santoro Exploring an Unknown Graph to Locate a Black Hole Using Tokens. 131-150 2006 IFIP TCS http://dx.doi.org/10.1007/978-0-387-34735-6_14 conf/ifipTCS/2006 db/conf/ifipTCS/ifipTCS2006.html#DobrevFKS06