@misc{151141,
  author = {Daniel Raviv},
  title = {Flat Surfaces: A Visual Invariant},
  year = {1992},
  month = {1992-03-31},
  publisher = {NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD},
  url = {https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=820398},
  language = {en},
}