To cite package ‘subtools’ in publications use:

  Keck F (2019). _subtools: Read and Manipulate Video Subtitles_. R
  package version 1.0, <https://github.com/fkeck/subtools>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {subtools: Read and Manipulate Video Subtitles},
    author = {Francois Keck},
    year = {2019},
    note = {R package version 1.0},
    url = {https://github.com/fkeck/subtools},
  }