To cite bgw estimation algorithms in publications use:

David S. Bunch, David M. Gay and Roy E. Welsch (1993). Algorithm 717-Subroutines for maximum likelihood and quasi-likelihood estimation of parameters in nonlinear regression models, ACM Transactions on Mathematical Software 19(1), 109-130. DOI 10.1145/151271.151279.

Corresponding BibTeX entry:

  @Article{,
    title = {Algorithm 717-Subroutines for maximum likelihood and
      quasi-likelihood estimation of parameters in nonlinear regression
      models},
    author = {David S. Bunch and David M. Gay and Roy E. Welsch},
    journal = {ACM Transactions on Mathematical Software},
    year = {1993},
    volume = {19},
    number = {1},
    pages = {21},
    doi = {10.1145/151271.151279},
    url = {https://dl.acm.org/doi/10.1145/151271.151279},
  }