Data is received that characterizes each of a plurality of documents within a document set. Based on this data, the plurality of documents are grouped into a plurality of stacks using one or more grouping algorithms. A prime document is identified for each stack that includes attributes representative of the entire stack. Subsequently, provision of data is provided that characterizes documents for each stack including at least the identified prime document to at least one human reviewer. User-generated input from the human reviewer is later received that categorized each provided document and data characterizing the user-generated input can then be provided. Related apparatus, systems, techniques and articles are also described.