Fougerolle spoke about the publishers book stamps from a vexillological perspective. His paper was entitled Ex-Libris and Vexillology. Those decorative labels on books typically are used to identify the owner. But many times over a heraldic style coat of arms is used, often including flags.
Fougerolle broke up the these book marks into five different categories: patriotic, military, heraldic, maritime, and artistic.