Konstantinos Kalpakis Yaacov Yesha Upper and Lower Bounds on the Makespan of Schedules for Tree Dags on Linear Arrays. 159-179 1999 23 Algorithmica 2 http://link.springer.de/link/service/journals/00453/bibs/23n2p159.html db/journals/algorithmica/algorithmica23.html#KalpakisY99