1. Theory of edge detection;Marr,1980
2. Implementation of a Theory of Edge Detection;Hildreth;M.I.T.A.I. Tech. Rep. TR-579,1980
3. Machine perception of three dimensional solids;Roberts,1965
4. Edge and Curve Enhancement in Digital Pictures;Rosenfeld;Univ. of Maryland Tech. Rep., 93,1969
5. On Boundary Detection;Herskovitz;M.I.T.A.I. Memo, No. 183,1970