@article{williams2015outlier,
  author = {James D. Williams and Jeffrey B. Birch and Abdel-Salam G. Abdel-Salam},
  title = {Outlier robust nonlinear mixed model estimation},
  year = {2015},
  journal = {Statistics in Medicine},
  volume = {34},
  number = {8},
  pages = {1304--1316},
  publisher = {Wiley},
  doi = {10.1002/sim.6406}
}