@misc{1202991,
  author = {Eyvon M Petty},
  title = {NIST time and frequency bulletin, no. 642:},
  year = {2011},
  month = {2011-01-01 05:01:00},
  publisher = {, National Institute of Standards and Technology, Gaithersburg, MD},
  doi = {https://doi.org/10.6028/NIST.IR.6661-06},
  language = {en},
}