Citation for finding node disjoint paths using maximum flow We can find  the maximum number of vertex disjoint paths in a directed graph using maximum flow algorithm keeping the node capacity and edge capacity to one. I could not find the reference paper for this technique. Please let me know the citation for this technique.
This reduction appears in §4 (Menger's theorem) of ON THE MAX-FLOW MIN-CUT THEOREM OF NETWORKS, G. B. Dantzig and D. R. Fulkerson without citation to another work. It's possible that this was a reinvention, but it's not clear to me where to look next.