@misc{indiciae7c2fd427938f,
  title = {Single-state selection system for hydrogen masers},
  author = {Mattison, Edward M. and Vessot, Robert F. C. and Shen, Wei},
  year = {1987},
  url = {https://ntrs.nasa.gov/citations/19880034319},
  note = {Source identifier: 19880034319}
}