Proc Natl Acad Sci U S A. 2006 Oct 3;103(40):14724-31 doi:10.1073/pnas.0508637103

Yu H, Gerstein M.

Genomic analysis of the hierarchical structure of regulatory networks.

Breadth-first search: organises a network in a layered hierarchy. Highest nodes tend to be influencial, middle to have a high betweenness, and lowest to be essential.