Stefan Harmeling Andreas Ziehe Motoaki Kawanabe Klaus-Robert Müller Kernel-Based Nonlinear Blind Source Separation. 1089-1124 2003 15 Neural Computation 5 http://neco.mitpress.org/cgi/content/abstract/15/5/1089 db/journals/neco/neco15.html#HarmelingZKM03