About the lower bounds for the number of additional arcs in a minimal vertex 1-extension of oriented path | Prikladnaya Diskretnaya Matematika - Applied Discrete Mathematics. 2013. № 6 (Приложение).

A graph G* with n + k vertices is vertex k-extension of a graph G if every graph obtained by removing any k vertices from G* contains G; it is called minimal vertex k-extension of G if it has the least number of arcs among all vertex k-extensions of graph G with n + k vertices. A lower bound for the number of additional arcs in minimal vertex 1-extension of an oriented path is given.