Analysis of information sources in references of the Wikipedia article "Bregman divergence" in English language version.
Supposed D_\varphi is a Bregman divergence, supposed that {C_k} is a finite collection of closed, convex sets whose intersection is nonempty. Given an input matrix Y our goal is to produce a matrix \mathbf{X} in the intersection that diverges the least from \textbf{Y}, i.e. to solve \min_{\mathbf{X} } D_\varphi(\mathbf{X};\mathbf{Y}) subject to \mathbf{X} \in \big\cap_k C_k. Under mild conditions, the solution is unique and it has a variational characterization analogous with the characterization of an orthogonal projection onto a convex set" (see s2.4, page 1125 for more)