1. The partial order of a polymatroid extreme point;Bixby,1982
2. Submodular functions, matroids, and certain polyhedra;Edmonds,1970
3. Matroids and the greedy algorithm;Edmonds;Mathematical Programming,1971
4. A min-max relation for submodular functions on graphs;Edmonds;Annals Discrete Math.,1977
5. Generalized polymatroids;Frank,1981