@misc{indiciaeec3122b401a2,
  title = {Frequency modulation at a moving material interface and a conservation law for wave number},
  author = {Kleinstein, G. G. and Gunzburger, M. D.},
  year = {1976},
  url = {https://ntrs.nasa.gov/citations/19760063661},
  note = {Source identifier: 19760063661}
}