Ofer Dekel Shai Shalev-Shwartz Yoram Singer The Forgetron: A Kernel-Based Perceptron on a Budget. 1342-1372 2008 37 SIAM J. Comput. 5 http://dx.doi.org/10.1137/060666998 db/journals/siamcomp/siamcomp37.html#DekelSS08