- INSTANCE: Graph , the edge weights , a polymatroid .
- SOLUTION: A tree in G such that , , connecting a given root to all vertices of a least one base of P.
- COST FUNCTION: .
- OBJECTIVE: Minimize.
*Approx.:*Approximable within for any ,

approximable within in quasi-polynomial time[24], [27].*Hardness:*NP-hard to approximate within for every [61], [24]*Comment:*The problem contains the Directed Steiner Tree Problem as a special case [24].

2015-04-27 Revision: 288 PDF version