To cite the penalized package in publications use:

  Jelle J. Goeman (2022). Penalized R package, version 0.9-52.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {Penalized: L1 (lasso and fused lasso) and L2 (ridge) penalized estimation in GLMs and in the Cox model},
    author = {J. J. Goeman and R. J. Meijer and N. Chaturvedi},
    year = {2022},
    note = {R package version 0.9-52},
  }

  Jelle J. Goeman (2010) L1 penalized estimation in the Cox
  proportional hazards model, Biometrical Journal, 52 (1) 80-84.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {L1 penalized estimation in the Cox proportional hazards model},
    author = {J. J. Goeman},
    journal = {Biometrical Journal},
    number = {52},
    issue = {1},
    pages = {-14},
    year = {2010},
  }