1. Computer-storage media storing computer-executable instructions that, when executed by a computing device, cause the computing device to perform a method of identifying, from within a corpus of documents, a subject that is relevant to a topic and that is usable to enhance a topic-describing document, the method comprising: retrieving the topic-describing document that describes the topic and a linked document that is hyperlinked to the topic-describing document and that describes a subject; parsing text of the linked document to identify the subject and to identify within the text of the linked document a data-page hyperlink that is associated with a date relevant to the subject and that navigates to a date-describing reference document; storing an association between the subject and the linked document, wherein the association enables retrieval of the linked document; determining that the subject in the linked document is relevant to the topic described by the topic-describing document by applying a set of one or more rules to at least content of the linked document and content of the topic-describing document, wherein a grammatical context of the subject in the linked document suggests a degree of relevance of the subject to the topic; utilizing an association between the subject and the linked document to retrieve the linked document when the subject represented by the linked document is deemed to be relevant to the topic described by the topic-describing document; analyzing metadata of the linked document that was retrieved to identify temporally significant information and location information of the subject; using the temporally significant information and the location information of the subject that was obtained from the metadata of the linked document to generate a timeline and a map depicting a geographic location of the subject; and transforming a first version of the topic-describing document into an enhanced version of the topic-describing document by inserting the timeline and the map into the first version.