Noga Alon Fedor V. Fomin Gregory Gutin Michael Krivelevich Saket Saurabh Parameterized Algorithms for Directed Maximum Leaf Problems. 352-362 2007 conf/icalp/2007 ICALP http://dx.doi.org/10.1007/978-3-540-73420-8_32 db/conf/icalp/icalp2007.html#AlonFGKS07