Jakub Pawlewicz Lukasz Lew Improving Depth-First PN-Search: 1 + <i>epsilon</i> Trick. 160-171 2006 conf/cg/2006 Computers and Games http://dx.doi.org/10.1007/978-3-540-75538-8_14 db/conf/cg/cg2006.html#PawlewiczL06