@misc{indiciae78edeeeeac1b,
  title = {Numerical method to calculate the induced drag or optimum loading for arbitrary non-planar aircraft},
  author = {Blackwell, J. A., Jr.},
  year = {1976},
  url = {https://ntrs.nasa.gov/citations/19760021079},
  note = {Source identifier: 19760021079}
}