9. A method of identifying one or more documents within a collection of documents, the method being performed by a computer system that comprises one or more processors, a memory operatively coupled to at least one of the processors, and a computer-readable storage medium encoded with instructions executable by at least one of the processors and operatively coupled to at least one of the processors, the method comprising: storing in the memory a search level that is a whole number that is at least two; storing in the memory a definition of a subset of a collection of electronic documents, the collection of documents comprising a plurality of documents, and the subset comprising one or more source documents within the collection and one or more additional documents within the collection, the one or more additional documents being identifiable by a process carried out for a number of iterations equal to the search level and comprising: (1) a first iteration that comprises finding one or more references in one or more of the electronic source documents, each of the references identifying a respective document in the collection, and adding to the subset each document in the collection that is identified by any of the found references but is not already in the subset, and (2) one or more subsequent iterations, each of which comprises finding one or more references in one or more of the documents added to the subset in the immediately previous iteration, each of the references identifying a respective document in the collection, and adding to the subset each document in the collection that is identified by any of the found references but is not already in the subset; at least one of the processors receiving through at least one interface operatively coupled to the processor a definition of a search query through an interlace operatively coupled to at least one of the processors, the search query comprising one or more criteria that a user has explicitly entered, and the search query having an association with a topical area for a search; at least one of the processors executing instructions retrieved from the computer-readable storage medium to (i) identify all responsive documents within the subset that satisfy the one or more criteria comprised by the search query such that each responsive document includes each of the one or more criteria of the search query, (ii) retrieve a definition of a search space, the definition of the search space comprising one or more normalized citations to every document within the search space, and the search space having an association with the topical area for the search, (iii) filter the responsive documents resulting from the execution of the search query by checking each responsive document against the definition of the search space and (iv) removing from further consideration an responsive document not found in the definition of the search space; and at least one of the processors executing instructions retrieved from the computer-readable storage medium to transmit through the at least one interface information for display to the user that identifies one or more of the remaining responsive documents.
9. A method of identifying one or more documents within a collection of documents, the method being performed by a computer system that comprises one or more processors, a memory operatively coupled to at least one of the processors, and a computer-readable storage medium encoded with instructions executable by at least one of the processors and operatively coupled to at least one of the processors, the method comprising: storing in the memory a search level that is a whole number that is at least two; storing in the memory a definition of a subset of a collection of electronic documents, the collection of documents comprising a plurality of documents, and the subset comprising one or more source documents within the collection and one or more additional documents within the collection, the one or more additional documents being identifiable by a process carried out for a number of iterations equal to the search level and comprising: (1) a first iteration that comprises finding one or more references in one or more of the electronic source documents, each of the references identifying a respective document in the collection, and adding to the subset each document in the collection that is identified by any of the found references but is not already in the subset, and (2) one or more subsequent iterations, each of which comprises finding one or more references in one or more of the documents added to the subset in the immediately previous iteration, each of the references identifying a respective document in the collection, and adding to the subset each document in the collection that is identified by any of the found references but is not already in the subset; at least one of the processors receiving through at least one interface operatively coupled to the processor a definition of a search query through an interlace operatively coupled to at least one of the processors, the search query comprising one or more criteria that a user has explicitly entered, and the search query having an association with a topical area for a search; at least one of the processors executing instructions retrieved from the computer-readable storage medium to (i) identify all responsive documents within the subset that satisfy the one or more criteria comprised by the search query such that each responsive document includes each of the one or more criteria of the search query, (ii) retrieve a definition of a search space, the definition of the search space comprising one or more normalized citations to every document within the search space, and the search space having an association with the topical area for the search, (iii) filter the responsive documents resulting from the execution of the search query by checking each responsive document against the definition of the search space and (iv) removing from further consideration an responsive document not found in the definition of the search space; and at least one of the processors executing instructions retrieved from the computer-readable storage medium to transmit through the at least one interface information for display to the user that identifies one or more of the remaining responsive documents. 10. The method of claim 9 , comprising: at least one of the processors executing instructions retrieved from the computer-readable storage medium to compute rankings of the identified responsive documents, the computed ranking of each respective identified responsive document depending at least upon the iteration in which that document would first be added to the subset; and at least one of the processors executing instructions retrieved from the computer-readable storage medium to transmit through one of the interfaces information that identifies a plurality of the responsive documents; wherein the provided information that identifies a plurality of the responsive documents comprises information about the ranking of the identified documents.