 Polynomial time algorithms are known for determining whether the derived graph of a formula_10-voltage graph contains any directed cycles.Any Cayley graph of a group Π, with a given set Γ of generators, may be defined as the derived graph for a Π-voltage graph having one vertex and |Γ| self-loops, each labeled with one of the generators in Γ.The Petersen graph is the derived graph for a ℤ5-voltage graph in the shape of a dumbbell with two vertices and three edges