1. J. Edmonds andR. Giles, A min-max relation for submodular functions on graphs, in: “Studies in integer programming” (Proc. Workshop on Integer Programming Bonn, 1975; P. L. Hammer, E. L. Johnson, B. H. Korte, eds.),Annals of Discrete Math. 1 (1977) 185–204.
2. L. R. Ford, Jr. andD. R. Fulkerson,Flows in Networks, Princeton Univ. Press, Princeton, N.J., 1962.
3. A. Frank, An algorithm for submodular functions on graphs, submitted toAnnals of Discrete Math.
4. S. Fujishige, Algorithms for solving the independent flow problems,J. Operation Res. Soc. Japan, Vol.21, No. 2, June (1978).
5. A. V. Karzanov, On the minimal number of arcs of a digraph meeting all its directed cutsets, (abstract)Graph Theory Newsletters, Vol.8 (No. 4) March 1979.