2. The system of claim 1 , wherein the metadata research module includes a learning machine for processing a set of feature vectors including one or more features from the group consisting of: a feature based on text similarity; a feature based on number of shared legal classification codes; and a feature based on number of shared legal citations.
8. The system of claim 2 , wherein the feature based on number of shared legal citations include one or more from the group consisting of NumSources, NumReasons, MaxQuotations, NumSourcesCiting, NumCitedSources, NumCoCitedCases, NumCoCitedByCases, Num SharedStatutes, and SimpleKeyciteCiteCount.