MINIMAL PRIMITIVE EXTENSIONS OF ORIENTED GRAPHS | Prikladnaya Diskretnaya Matematika - Applied Discrete Mathematics. 2008. № 1(1).

(Oriented) graph G = (V, α) is called primitiveif there exists an integer r ≥ 1 such that every two vertices can be connected by a route of length r. A graph G′ = (V, α) is saidto be a primitive extension of G if G' is primitive and α ⊆ α′. Primitive extensions with a minimal possible number of additionalarcs are constructed for some acyclic graphs (trees, linear and polygonal graphs)