Yossi Azar Uriel Feige Daniel Glasner A Preemptive Algorithm for Maximizing Disjoint Paths on Trees. 319-330 2008 SWAT http://dx.doi.org/10.1007/978-3-540-69903-3_29 conf/swat/2008 db/conf/swat/swat2008.html#AzarFG08