The circular chromatic number of induced subgraphs
For positive integers \(d\) and \(k\), \(k\geq 2d\), a \((k, d)\)-coloring of a graph \(G\) is a mapping \(f: V(G) \rightarrow \{0, \dots, k-1\}\) such that, for every adjacent vertices \(x, y\) of \(G\), \(d\leq | f(x) - f(y)| \leq k - d\). The circular chromatic number of \(G\) is \(\chi_c(G) =\min\{\frac{k}{d} : G \text{ admits a }(k, d)\)-coloring
scientific article; zbMATH DE number 2104556