To cite ptmixed in publications use:

  Signorelli, M., Spitali, P., Tsonaka, R. (2021). Poisson-Tweedie
  mixed-effects model: a flexible approach for the analysis of
  longitudinal RNA-seq data. Statistical Modelling, 21 (6), 520-545.
  URL: https://doi.org/10.1177/1471082X20936017, DOI:
  10.1177/1471082X20936017

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Poisson-Tweedie mixed-effects model: a flexible approach for the analysis of longitudinal RNA-seq data},
    author = {{Signorelli} and {M.} and {Spitali} and {P.} and {Tsonaka} and {R.}},
    journal = {Statistical Modelling},
    volume = {21},
    number = {6},
    pages = {520--545},
    year = {2021},
    url = {https://doi.org/10.1177/1471082X20936017},
  }