Fuzzy rectangles

Rosenfeld, 1984, The fuzzy geometry of image subsets, Pattern Recognition Letters, 2, 311, 10.1016/0167-8655(84)90018-7

Rosenfeld, 1979, Fuzzy digital topology, Information and Control, 40, 76, 10.1016/S0019-9958(79)90353-X

Zadeh, 1965, Fuzzy sets, Information and Control, 8, 338, 10.1016/S0019-9958(65)90241-X

Rosenfeld, 1985, The perimeter of a fuzzy set, Pattern Recognition, 18, 125, 10.1016/0031-3203(85)90035-4