To cite package ‘multpois’ in publications use:

  Wobbrock J (????). _multpois: Analyze Nominal Response Data with the
  Multinomial-Poisson Trick_. R package version 0.2.0,
  <https://github.com/wobbrock/multpois>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {{multpois}: Analyze Nominal Response Data with the Multinomial-Poisson Trick},
    author = {Jacob O. Wobbrock},
    note = {R package version 0.2.0},
    url = {https://github.com/wobbrock/multpois},
  }