@misc{indiciaea91759b48aff,
  title = {Counter-rotating propeller noise directivity and trends},
  author = {Block, P. J. W. and Klatte, R. J. and Druez, P. M.},
  year = {1986},
  url = {https://ntrs.nasa.gov/citations/19860060680},
  note = {Source identifier: 19860060680}
}