@article{90771,
  author = {Steven Fick},
  title = {Long-term Stability of the NIST Standard Ultrasonic Source},
  year = {2008},
  number = {113},
  month = {2008-10-01},
  publisher = {Journal of Research of the National Institute of Standards and Technology},
  url = {https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=824662},
  language = {en},
}