1. A computer-implemented method comprising: accessing a corpus stored in one or more tangible media, the corpus comprising a plurality of documents, a document comprising a plurality of words; selecting one or more words of each document as one or more keywords of the each document; clustering the documents according to the keywords to yield a plurality of clusters, each cluster corresponding to a different topic; generating a statistical distribution for each cluster from a subset of the words of the documents of the each cluster to yield a plurality of statistical distributions, wherein generating the statistical distribution for the each cluster comprises: determining a co-occurrence value indicating a co-occurrence of the topic of the each cluster with the topics of the other clusters in the plurality of documents; and generating a co-occurrence distribution from the co-occurrence values; modeling each topic using the statistical distribution generated for the cluster corresponding to the each topic; organizing the clusters according to the statistical distributions; and assigning the topics of the organized clusters to the documents in the organized clusters.