The aromaticity in local rings of polycyclic compounds can be assessed by the Glidewell-Lloyd rule (GLR), which is the generalized form of the famous Clar's rule to adjust for heterocyclic and polycyclic systems with different ring sizes. According to the GLR in conjugated polycyclic aromatic systems, the larger rings lose their aromaticity in favor of smaller ones. In a recent study, Pino-Rios and Solà proved that the 5-membered ring in isoindole and indolizine is more aromatic than the 6-membered ring, which is in line with the GLR. Indole on the other hand has a relatively more aromatic 6-membered ring because it can benefit from a unique resonance structure in which both the 5-and 6-membered rings possess 6 π-electrons.