Ichihara, Kazuhiro y Ushijima, Akira. 2008. Strongly Invertible Knots, Rational-Fold Branched Coverings, and Hyperbolic Spatial Graphs. Revista Matemática Complutense 21, 2, 435–451. DOI:https://doi.org/10.5209/rev_REMA.2008.v21.n2.16395