@article{39371,
  author = {Michael Lombardi},
  title = {The Evolution of Time Measurement: Part 3 - Atomic Clocks; The Evolution of Time Measurement: Part 4 - Atomic Second},
  year = {2012},
  number = {15},
  month = {2012-02-01},
  publisher = {IEEE Instrumentation and Measurement Magazine},
  language = {en},
}