@misc{indiciaeb20ead0ed3be,
  title = {Frequency tracked gated pulse technique for ultrasonic frequency},
  author = {Cantrell, Jr., John H. and Heyman, Joseph S.},
  year = {1983},
  url = {https://ntrs.nasa.gov/citations/20080005880},
  note = {Source identifier: 20080005880}
}