According to the solution of this problem (Trahtman 2009), a strongly connected directed graph in which all vertices have the same outdegree has a synchronizable edge coloring if and only if it is aperiodic.
Prema rešenju ovog problema (Trahtman 2009), čvrsto povezan usmeren graf u kojem svi čvorovi imaju isti izlazni stepen, ima sinhrozabilnu granu bojanja ako i samo ako je aperiodičan.