To cite the Inverse Gaussian and GL Type 1 shared frailty models with
Generalized Weibull baseline:

  Pandey A, Hanagal D, Tyagi S (2022). “Shared Frailty Models Based on
  Cancer Data.” _International Journal of Statistics and Reliability
  Engineering_, *9*(3), 461-474.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Shared Frailty Models Based on Cancer Data},
    author = {Arvind Pandey and David D. Hanagal and Shikhar Tyagi},
    journal = {International Journal of Statistics and Reliability Engineering},
    year = {2022},
    volume = {9},
    number = {3},
    pages = {461--474},
  }

To cite the GL Type 2 and Gamma shared frailty models with Weibull
baseline:

  Pandey A, Tyagi S (2021). “Comparison of Multiplicative Frailty
  Models Under Weibull Baseline Distribution.” _Lobachevskii Journal of
  Mathematics_, *42*(13), 3184-3195. doi:10.1134/S1995080222010140
  <https://doi.org/10.1134/S1995080222010140>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Comparison of Multiplicative Frailty Models Under Weibull Baseline Distribution},
    author = {Arvind Pandey and Shikhar Tyagi},
    journal = {Lobachevskii Journal of Mathematics},
    year = {2021},
    volume = {42},
    number = {13},
    pages = {3184--3195},
    doi = {10.1134/S1995080222010140},
  }