A 3x3 Isotropic Gradient Operator for Image Processing presented at a talk at the Stanford Artificial Project in 1968, by I. Sobel and G. Feldman.

A Computational Approach To Edge Detection, IEEE Trans. Pattern Analysis and Machine Intelligence, by Canny, J.

Robust Detection of Lines Using the Progressive Probabilistic Hough Transform, CVIU 78 1, by Matas, J. and Galambos, C., and Kittler, J.V. pp 119-137 (2000).

Advanced High Dynamic Range Imaging: Theory and Practice, CRC Press, by Banterle, Francesco; Artusi, Alessandro; Debattista, Kurt; Chalmers, Alan.