This implements topics that change over time (Dynamic Topic Models) and a model of how individual documents predict that change. This code is the result of work by David M. Blei and Sean M. Gerrish. (C) Copyright 2006, David M. Blei (C) Copyright 2011, Sean M. Gerrish It includes software corresponding to models described in the following papers: [1] D. Blei and J. Lafferty. Dynamic topic models.