Klaus Jansen Lars Prädel Ulrich M. Schwarz Two for One: Tight Approximation of 2D Bin Packing. 399-410 2009 WADS http://dx.doi.org/10.1007/978-3-642-03367-4_35 conf/wads/2009 db/conf/wads/wads2009.html#JansenPS09