An Oracle Inequality for Quasi-Bayesian Non-Negative Matrix   Factorization
  The aim of this paper is to provide some theoretical understanding of quasi-Bayesian aggregation methods non-negative matrix factorization. We derive an oracle inequality for an aggregated estimator. This result holds for a very general class of prior distributions and shows how the prior affects the rate of convergence. 
Pierre Alquier and Benjamin Guedj
stat.ML math.ST stat.TH