@misc{indiciaec47d8e539f08,
  title = {Recent Langley helicopter acoustics contributions},
  author = {Morgan, Homer G. and Pao, S. P. and Powell, C. A.},
  year = {1988},
  url = {https://ntrs.nasa.gov/citations/19880007263},
  note = {Source identifier: 19880007263}
}