@misc{63301,
  author = {F Walls and Eva Ferre-Pikal},
  title = {Frequency Standards, Characterization,},
  year = {1999},
  number = {12},
  month = {1999-01-01},
  publisher = {Wiley Encyclopedia of Electrical and Electronics Engineering},
  url = {https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=105599},
  language = {en},
}