Adam Tauman Kalai Adam R. Klivans Yishay Mansour Rocco A. Servedio Agnostically Learning Halfspaces. 1777-1805 2008 37 SIAM J. Comput. 6 http://dx.doi.org/10.1137/060649057 db/journals/siamcomp/siamcomp37.html#KalaiKMS08