1. A method executed by a computer processor, the method comprising: receiving a request for a co-citation graph for a first research document, wherein the first research document has an author and includes citations to other research documents; executing a search over contents of a data repository responsive to receiving the request, the data repository comprises a plurality of research documents including the first research document; and based at least in part upon executing the search, causing the co-citation graph to be presented on a display of a computing device, the co-citation graph presented on the display comprises: a first node that is representative of the first research document; a second node that is representative of a second research document; a plurality of nodes that are respectively representative of a plurality of other research documents, each research document in the plurality of other research documents comprising sentences that include citations to the first research document and the second research document; and graphical data that indicates that each research document in the plurality of other research documents comprises the sentences that include the citations to the first research document and the second research document.