1. Solutio Problematis ad geometriam situs pertinensis;Euler;Commentarii Academiae Scientiarum Imperialis Petropolitanae,1736
2. On random graphs;Erdos;Pub. Mathem.,1959
3. Connectivity of random nets;Solomonoff;Bull. Math. Biophys.,1951
4. On the theory of analytic forms called trees;Cayley;Philos. Mag.,1857
5. The small-world problem;Milgram;Psychology Today,1967