@misc{indiciae57e80e16856a,
  title = {A simple approach to nonlinear estimation of physical systems},
  author = {G. Christakos},
  year = {1988},
  doi = {10.1016/0895-7177(88)90560-2},
  url = {https://pubs.usgs.gov/publication/70013356},
  note = {Source identifier: 70013356}
}