Matthias Baumgart Stefan Eckhardt Jan Griebsch Sven Kosub Johannes Nowak All-Pairs Ancestor Problems in Weighted Dags. 282-293 2007 conf/escape/2007 ESCAPE http://dx.doi.org/10.1007/978-3-540-74450-4_26 db/conf/escape/escape2007.html#BaumgartEGKN07