@article{206991,
  author = {Steven Jefferts and Thomas Heavner and Thomas Parker and Jon Shirley},
  title = {NIST Cesium Fountains – Current Status and Future Prospects},
  year = {2007},
  number = {6673},
  month = {2007-09-12},
  publisher = {Proceedings of the SPIE: Time and Frequency Metrology},
  url = {https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50590},
  language = {en},
}