El Bachir Ameur Domingo Barrera María J. Ibáñez Driss Sbibih Near-best operators based on a <i>I</i> quartic spline on the uniform four-directional mesh. 151-160 2008 77 Math. Comput. Simul. 2-3 https://doi.org/10.1016/j.matcom.2007.08.005 db/journals/mcs/mcs77.html#AmeurBIS08