@misc{204106,
  author = {J McCracken},
  title = {NIST Metric Pyramid},
  year = {2002},
  month = {2002-04-01},
  publisher = {Letter Circular, National Institute of Standards and Technology, Gaithersburg, MD},
  doi = {https://doi.org/10.6028/NIST.LCIRC.1140},
  language = {en},
}