Complexity of colouring problems restricted to unichord-free and \{square,unichord\}-free graphs

Raphael C. S. Machado, Celina M. H. de Figueiredo, Nicolas Trotignon

A \emph{unichord} in a graph is an edge that is the unique chord of a cycle. A \emph{square} is an induced cycle on four vertices. A graph is \emph{unichord-free} if none of its ed…