No CrossRef data available.
Published online by Cambridge University Press: 18 May 2009
All graphs considered in this article are finite connected, without loops and multiple edges. Let G be a graph and x be a vertex. The vertex neighbourhood graph (or υ-neighbourhood) of x in G (denoted by is the subgraph of G induced by the set of all vertices of G adjacent to x Analogously if f = xy is any edge of G, the edge neighbourhood graph (or e-neighbourhood) of f in G is the subgraph of G (denoted
or
induced by the set of all vertices of G which are adjacent to at least one vertex of the pair x, y and are different from x, y.