1. Gibson, J.J.: ‘The perception of the visual world’, (Houghton-Mifflin, Boston 1950)
2. Texture gradient as a depth cue
3. Horn, B.K.P.: ‘Obtaining shape from shading information’, Winston, P.H., The psychology of computer vision, (McGraw-Hill, New York 1975), p. 115–155
4. Shape from focus