István Estélyi: A construction of half-arc-transitive graphs

Povzetek. A graph, the automorphism group of which has a subgroup that acts transitively on the set of vertices and on the set of edges, but not on the set of arcs is called a half-arc-transitive graph. In the presentation we provide Brouwer's construction of a half-arc-transitive graph for every even valency (i.e., every possible valency).