@string{ai   = "Artificial Intelligence"}
@string{cvgip = "Computer Vision, Graphics, and Image Processing"}

@incollection{Horn75,
author = "B. K. P. Horn",
title = "Obtaining shape from shading information",
booktitle = "The Psychology of Computer Vision",
editor = "P. H. Winston",
publisher = "McGraw-Hill",
address = "New York, NY",
year = 1975,
pages = "115-155"
}

@article{Horn77,
author = "B. K. P. Horn",
title = "Understanding image intensities",
journal = ai,
volume = 8,
pages = "201-231",
year =  1977
}

@book{HornBrooks89,
author="B. K. P. Horn and M. Brooks",
title="Seeing shape from shading",
publisher = "MIT Press",
address = "Cambridge, Mass.",
year = 1989
}

@Article{KnillKersten90,
  author = 	 "D. C. Knill and D. Kersten",
  title = 	 "Learning a {near-optimal} estimator for surface shape
		  from shading",
  journal =	 cvgip,
  year =	 1990,
  volume =	 50,
  pages =	 "75-100",
  annote =	 "solution in terms of linear RFs, as in Hurlbert and
		  Poggio, 1988"
}