Markus Chimani Carsten Gutwenger Petra Mutzel Hoi-Ming Wong Layer-Free Upward Crossing Minimization. 55-68 2008 WEA http://dx.doi.org/10.1007/978-3-540-68552-4_5 conf/wea/2008 db/conf/wea/wea2008.html#ChimaniGMW08