@misc{indiciaeaf171bb6adca,
  title = {Nonparametric estimation of covariance structure in longitudinal data.},
  author = {P J Diggle and A P Verbyla},
  year = {1998},
  url = {https://pubmed.ncbi.nlm.nih.gov/9629635/},
  note = {Source identifier: 9629635}
}