Ivana Ljubic René Weiskircher Ulrich Pferschy Gunnar W. Klau Petra Mutzel Matteo Fischetti Solving the Prize-Collecting Steiner Tree Problem to Optimality. 68-76 2005 conf/alenex/2005 ALENEX/ANALCO http://www.siam.org/meetings/alenex05/papers/06iljubic.pdf db/conf/alenex/alenex2005.html#LjubicWPKMF05