This is the output from a program of Jon Kleinberg of Cornell's CS department
which is designed to find the "authoritative" web sites on a subject. It
begins by finding the top 200 odd sites given by a standard search engine,
but these are often a somewhat random collection of sites referring to the
topic. The program then takes these sites and all sites with pointers
sites and builds a directed graph of pointers. Then within this graph (whose
node set is a longer
list of sites, typically around 5000), it looks for small tightly-linked
subgraphs. Those that point to others are called "hubs", and those
that are pointed to are called "authorities." This is all done by looking
at the eigenvalues and eigenvectors of the directed graph.
Further information (subgroups, or communities within the set of hubs and authorities) are obtained by looking at eigenvalues other than the dominant one. Details on the approach can be found here.
The sites below were obtained by making an initial search on "+semidefinite+programming."