@conference{104216,
  author = {Neil Ashby and Thomas Heavner and Steven Jefferts and A Radnaev and Y Dudin},
  title = {Testing Local Position Invariance with Four H Masers AND Four Cs Fountains},
  year = {2007},
  month = {2007-05-28},
  publisher = {Proc. 2007 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and EFTF Conf., Geneva, CH},
  url = {https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50569},
  language = {en},
}