OK, I admit I have no idea what is the correct terminology, so could be thread title is completely off. Imagine I have a graph of links between www pages. I suppose some of these pages are clustered - that is, they are heavily interlinked, but they don't link so extensively to other clusters/pages. How do I find them? This is not different from finding groups of friends in some population by analysing phone calls and so on. I am more than sure that I have seen pictures showing results of such analysis (perhaps in Scientific American), but I can't remember any details, I am even not sure about correct terminology. Fact that I have probably read about the problem in Polish doesn't help either. Names, links, keywords to look for will be appreciated.