Search may be provided using a database storing a plurality of documents comprising a first set of documents and a second set of documents, a set of vetting values and a computer readable medium. In such a system, for each document in the second set of documents, the first set of documents comprises a document for which that document from the second set of documents is identified as a subsequent related document. Additionally, the set of vetting values may comprise, for each document from the second set of documents, a vetting value for the document from the first set of documents for which that document from the second set of documents is identified as the subsequent related document. Additionally, the medium may store instructions to respond to a query by determining, based on the set of vetting values, a search result set comprising documents from the first set of documents.