@misc{indiciaeb21af1029a7d,
  title = {Hydrogen maser frequency comparison with a cesium beam standard},
  author = {Johnson, E. H. and Mc Gunigal, T. E.},
  year = {1966},
  url = {https://ntrs.nasa.gov/citations/19660012409},
  note = {Source identifier: 19660012409}
}