This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Periodgraph.svg stronglyconnected graph in which all cycle lengths are divisible by three Therefore this graph is not aperiodic en David Eppstein en David Eppstein original upload log page en Periodgraph David Eppstein bytes no stronglyconnected graph in which all cycle lengths are divisible by three Therefore this graph