@misc{indiciaedf1b07e48da1,
  title = {A trigonometric method for monitoring ground-tilt changes on composite volcanoes},
  author = {John W. Ewert},
  year = {1989},
  doi = {10.3133/ofr89223},
  url = {https://pubs.usgs.gov/publication/ofr89223},
  note = {Source identifier: ofr89223}
}