@misc{indiciae5780e4aee429,
  title = {Acoustic radiation from lined unflanged ducts: Directivity index program},
  author = {Beckemeyer, R. J. and Sawdy, D. T.},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19750020777},
  note = {Source identifier: 19750020777}
}