@misc{indiciae815e0898502c,
  title = {Modified bubble level senses pitch and roll angles over wide range},
  author = {Mattson, E. J. and Mcnally, P. F.},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19710000084},
  note = {Source identifier: 19710000084}
}