Hyeyoung Park Noboru Murata Shun-ichi Amari Improving Generalization Performance of Natural Gradient Learning Using Optimized Regularization by NIC. 355-382 2004 16 Neural Computation 2 http://neco.mitpress.org/cgi/content/abstract/16/2/355 db/journals/neco/neco16.html#ParkMA04