@misc{indiciaed914bebfcf77,
  title = {Physical constraints on sounds generated by very small earthquakes},
  author = {David P. Hill},
  year = {1976},
  doi = {10.3133/ofr7620},
  url = {https://pubs.usgs.gov/publication/ofr7620},
  note = {Source identifier: ofr7620}
}