For decentralized routing, Kleinberg has a wonderfully lucid paper in Science in 2000 that's one page long (something like "navigation in a small world"). Essen

For decentralized routing, Kleinberg has a wonderfully lucid paper in Science in 2000 that's one page long (something like "navigation in a small world"). Essentially, even though short paths may exist in a network, it's hard for any decentralized routing algorithm (like the one in Milgram's experiment) to find them.