Yegui Xiao Rabab Kreidieh Ward Akira Ikuta Steady-state properties of the sign algorithm for the constrained adaptive IIR notch filter. 25-28 2003 ISCAS (4) http://dx.doi.org/10.1109/ISCAS.2003.1205764 db/conf/iscas/iscas2003-4.html#XiaoWI03