The anthracene molecule admits three resonance structures, each with a circle in one ring and two sets of double bonds in the other two. Following the rule at point 4 exposed above, anthracene is better described by a superposition of these three equivalent structures, and an arrow is drawn to indicate the presence of a migrating π-sextet. Following the same line of reasoning, one can find migrating π-sextets in other molecules of the acene series, such as tetracene, pentacene, and hexacene.