In this paper we determine the maximum number of edges that a strong digraph can have if it has a unique minimally strong subdigraph. We show that this number equals n(n-1)/2+1. Furthermore we show that there is, up to an isomorphism, a unique strong digraph which attains this maximum. © 1988.
Brualdi, R. A., & Manber, R. (1988). On strong digraphs with a unique minimally strong subdigraph. Discrete Mathematics, 71(1), 1–7. https://doi.org/10.1016/0012-365X(88)90025-8