@misc{indiciaef4f0bb2473b6,
  title = {An efficient, direct finite difference method for computing sound propagation in arbitrarily shaped two-dimensional and axisymmetric ducts without flow},
  author = {Chakravarthy, S.},
  year = {1978},
  url = {https://ntrs.nasa.gov/citations/19780040117},
  note = {Source identifier: 19780040117}
}