On minimal strong blocks
Martin Grötschel · Journal of Graph Theory · 1979
Abstract It is shown that storng blocks, i.e., digraphs that are strongly connected and have no cutnodes have an ear‐decomposition. This result is used to prove that the number q of arcs of minimal strong blocks is bounded by p ≤ q ≤ 2p – 3 and that minimal strong blocks contain at least two nodes with indegree and outdegree equal to one.