Circulant covers of trivalent circulants

Given two graphs G1G1 and G2G2, one may ask whether or not G2G2 is a cover   of G1G1. Feng and Kwak [Typical circulant double coverings of a circulant graph, Discrete Math. 277 (2004) 73–85] provide a description of typical covers of a circulant graph by another circulant graph, and use other techniques to show that there are no double covers of trivalent circulant graphs. The purpose of this paper is to provide a description of all circulant covers over trivalent circulant graphs.