To cite package ‘WH’ in publications use:

  Guillaume Biessy (2023). “Revisiting Whittaker-Henderson Smoothing.”
  Working Paper.

A BibTeX entry for LaTeX users is

  @Unpublished{,
    title = {Revisiting Whittaker-Henderson Smoothing},
    author = {{Guillaume Biessy}},
    note = {Working Paper},
    year = {2023},
  }