Abstract.For two vertices 𝑢 and 𝑣 of a graph 𝐺, the set 𝐼[𝑢, 𝑣] consists of all vertices lying on some 𝑢 - 𝑣 geodesic in 𝐺. If 𝑆 is a set of vertices of 𝐺, then 𝐼[𝑆] is the union of all ...