1. A method comprising: receiving data characterizing each of a plurality of documents within a document set; grouping the plurality of documents into a plurality of stacks using one or more grouping algorithms; identifying a prime document for each stack, the prime document including attributes representative of the entire stack; providing data characterizing documents for each stack including at least the identified prime document to at least one human reviewer; receiving user-generated input from the human reviewer categorizing each provided document; and providing data characterizing the user-generated input.