@article{woo-94-grcvph,
  author = {Robert J. Woodham},
  title = {Gradient and Curvature from the Photometric Stereo Method, Including Local Confidence Estimation},
  journal = {Journal of the Optical Society of America, Series A},
  volume = {11},
  number = {11},
  pages = {3050--3068},
  year = 1994,
  altkeys = {wood-1994}
}