1. Digital detection of pits, peaks, ridges and ravines;Johnston;IEEE Trans. on Systems, Man and Cybernetics SMC,1975
2. Detection of surface-specific points by local parallel processing of discrete terrain elevation data;Peucker;Computer Graphics and Image Processing,1975
3. Detection of surface-specific points by local parallel processing of discrete terrain elevation data;Peucker;Univ. of Maryland, Computer Science Center, Tech. Rep. TR-206,1972
4. A mathematical model for the analysis of contour-line data;Morse;J. Assoc. Comput. Mach.,1968
5. Structure lines of images;Enomoto,1976