A search system generates a plurality of pseudo-documents for a set of documents. Each pseudo-document includes a representation one or more documents from the set of documents that would be retrieved in response to executing a respective basis query over the set of documents. The search system generates an index of the plurality of pseudo-documents. The index provides an indication, for a plurality of respective documents from the set of documents, of the pseudo-documents that include a representation of the respective document. After generating the index, the search system receives a document-query that includes a representation of a first document; and in response to receiving the document-query, the search system identifies one or more pseudo-documents that include representations of at least one document having a predefined relationship to the first document; and generates a result that is based on the first set of one or more pseudo-documents.