Coloring rings

Frédéric Maffray, Irena Penev, Kristina Vušković

A ring is a graph $R$ whose vertex set can be partitioned into $k\ge 4$ nonempty sets, $X_1,\dots ,X_k$, such that for all $i\in \{1,\dots ,k\}$, the set $X_i$ can be ordered as…