Rein van den Boomgaard Joost van de Weijer Least Squares and Robust Estimation of Local Image Structure. 237-254 2003 conf/scalespace/2003 Scale-Space http://link.springer.de/link/service/series/0558/bibs/2695/26950237.htm db/conf/scalespace/scalespace2003.html#BoomgaardW03