@misc{1183236,
  author = {Daniel J Chwirut},
  title = {Recent improvements to the ASTM-type ultrasonic reference block system:},
  year = {1979},
  month = {1979-01-01 05:01:00},
  publisher = {, National Institute of Standards and Technology, Gaithersburg, MD},
  doi = {https://doi.org/10.6028/NBS.IR.79-1742},
  language = {en},
}