Some embodiments provide a machine-implemented method. The method identifies an event for a particular category based on a number of documents classified as relevant to the particular category in a particular period of time. Based on content of the documents classified as relevant to the particular category, the method identifies a set of keywords for the event. The method uses the keywords to automatically select a representative document for the event. Some embodiments store a link to the representative document and automatically determine whether the particular document is still accessible at the link. When the document is no longer accessible at the link, the method replaces the document with a backup document as the representative document for the event.