1. A computer-implemented method, comprising: identifying, by a device, a set of documents; expanding, by the device, the set of documents to generate an expanded set of documents, where the expanded set of documents includes all of the documents in the set of documents and one or more additional documents, and where each additional document, of the one or more additional documents, links to a document in the set of documents or is linked to by a document in the set of documents; determining, by the device, a similarity measure for each pair of documents in the expanded set of documents, where, for a pair of documents, in the expanded set of documents, consisting of a first document and a second document, the similarity measure is determined based on: a quantity of documents in the expanded set of documents that contain both a forward link to the first document and a forward link to the second document, whether the first document contains a forward link to the second document, and whether the second document contains a forward link to the first document; and clustering, by the device, the documents in the expanded set of documents into a plurality of clusters based on the similarity measures.
10. The computer-implemented method of claim 1 , where clustering the documents comprises: generating initial groups of documents, in the expanded set of documents, based on the similarity measures; determining a group similarity measure for each pair of groups of documents in the initial groups of documents, where, for a pair of groups of documents, in the initial groups of documents, consisting of a first group of documents and a second group of documents, the group similarity measure is determined based on a quantity of documents, in the expanded set of documents, that contain a forward link to a document in the first group of documents and contain a forward link to a document in the second group of documents; and clustering the initial groups of documents based on the group similarity measures.