1. Finding edges in noisy scenes;Machuca;IEEE Trans. Pattern Anal. Mach. Intell.,1981
2. Using angular dispersion of gradient direction for detecting edge ribbons;Gregson;IEEE Trans. Pattern Anal. Mach. Intell.,1993
3. Local orientation analysis in images by means of the Hermite transform;Martens;IEEE Trans. Image Process.,1997
4. “Machine perception of 3-D solids” ser;Roberts,1965
5. J. Matthews. “An introduction to edge detection: The sobel edge detector,” Available at http:// www. generation5.org/content/2002/ im01.asp, 2002.