Proc Natl Acad Sci U S A. 2005 May 31;102(22):7794-9. doi:10.1073/pnas.0407994102

Guimerà R, Mossa S, Turtschi A, Amaral LA.

The worldwide air transportation network: Anomalous centrality, community structure, and cities' global roles.

The muticommunauty structure of the air transortation network explains why some cities with a high centrality are not hubs.