13. A computer-system for rapidly identifying and ranking relevant documents from a body of citationally related documents, said computer system comprising: a computer-accessible index, stored in a physical data store, comprising identification information identifying multiple potential input documents from said body of citationally related documents and, for each said potential input document, identification information identifying a selected number of citationally related potential output documents from said body of citationally related documents, said computer-accessible index further comprising for each possible pair of citationally related potential input document and potential output document a first numerical score that is statistically correlated to the probability that a direct citation exists between said corresponding pair of citationally related documents; wherein said first numerical score is determined based at least in part on how many indirect citations exist between each potential input document and each potential output document and, for each indirect citation, how many citation links separate each potential input document from each potential output document; an input interface configured to enable a user to select a first set of identification information identifying one or more input documents from said body of citationally related documents for which relevant output documents are sought; a computer processor configured to: access, from said computer-accessible index, said first set of identification information to identify a selection of citationally related output documents; and calculate, for each identified output document, a second numerical score that is statistically correlated to the probability that a direct citation exists between any input document and each said corresponding output document, and wherein said second numerical score is determined based at least in part on said first numerical score; and an output interface configured to display a second set of identification information identifying a selected number of said identified output documents selected or ranked in accordance with said second numerical score.
13. A computer-system for rapidly identifying and ranking relevant documents from a body of citationally related documents, said computer system comprising: a computer-accessible index, stored in a physical data store, comprising identification information identifying multiple potential input documents from said body of citationally related documents and, for each said potential input document, identification information identifying a selected number of citationally related potential output documents from said body of citationally related documents, said computer-accessible index further comprising for each possible pair of citationally related potential input document and potential output document a first numerical score that is statistically correlated to the probability that a direct citation exists between said corresponding pair of citationally related documents; wherein said first numerical score is determined based at least in part on how many indirect citations exist between each potential input document and each potential output document and, for each indirect citation, how many citation links separate each potential input document from each potential output document; an input interface configured to enable a user to select a first set of identification information identifying one or more input documents from said body of citationally related documents for which relevant output documents are sought; a computer processor configured to: access, from said computer-accessible index, said first set of identification information to identify a selection of citationally related output documents; and calculate, for each identified output document, a second numerical score that is statistically correlated to the probability that a direct citation exists between any input document and each said corresponding output document, and wherein said second numerical score is determined based at least in part on said first numerical score; and an output interface configured to display a second set of identification information identifying a selected number of said identified output documents selected or ranked in accordance with said second numerical score. 19. The computer system of claim 13 wherein said output interface is configured to visually display said second set of identification information in the form of a self-organizing map.