@misc{228881,
  author = {Michael Lombardi},
  title = {A Historical Review of U. S. Contributions to the Atomic Definition of the SI Second},
  year = {2017},
  number = {122},
  month = {2017-06-01},
  publisher = {Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD},
  doi = {https://doi.org/10.6028/jres.122.029},
  language = {en},
}