@conference{9221,
  author = {Judah Levine and M. Weiss and D. Davis and D. Allan and D. Sullivan},
  title = {The NIST digital time service},
  year = {1989},
  url = {http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA520208},
  note = {JILA Pub. 4661},
}