1. A computer-implemented method for measuring or analyzing a degree of relevance between two or more citationally related documents, the method comprising: receiving a first set of identification information identifying two or more input documents for which a first generation relatedness score is sought; using said first set of identification information to access a stored computer-accessible database to produce a second set of identification information identifying one or more citationally related documents, said one or more citationally related documents being citationally related to said at least two or more input documents at a first or higher generation citational relationship; assigning a first generation relatedness score to said two or more input documents, said first generation relatedness score being calculated by a computer at least in part by counting a number of shared citational relationships occurring between said two or more input documents and said one or more citationally related documents at second generations or higher, said first generation relatedness score being statistically calculated by said computer to estimate an event probability that said at least two or more of said input documents are citationally related to one another at a first generation which is indicative of whether a first generation citational relationship exists between said two or more input documents, wherein first generational relationships exist between documents when a first document directly cites to a second document, wherein second generational or higher relationships exist between the first document and a third document when the first document cites to one or more intervening documents that cite to the third document; and outputting the first generation relatedness score between said two or more input documents.