To cite cfda, use:

Cristian Preda, Quentin Grimonprez, Vincent Vandewalle (2021). “Categorical Functional Data Analysis. The cfda R Package.” Mathematics, 9(23). doi:10.3390/math9233074. https://www.mdpi.com/2227-7390/9/23/3074.

Corresponding BibTeX entry:

  @Article{,
    title = {Categorical Functional Data Analysis. The cfda R Package},
    author = {{Cristian Preda} and {Quentin Grimonprez} and {Vincent
      Vandewalle}},
    journal = {Mathematics},
    year = {2021},
    volume = {9},
    number = {23},
    url = {https://www.mdpi.com/2227-7390/9/23/3074},
    doi = {10.3390/math9233074},
  }