To cite package 'season' in publications use:

Adrian G Barnett and Annette J Dobson (2010) Analysing Seasonal Health Data. Springer. Berlin, Heidelberg.
Adrian G Barnett and Peter J Baker and Annette J Dobson (2-01). season: Analysing Seasonal Data R Functions. R package version 0.3-1.

Corresponding BibTeX entries:

  @Book{,
    title = {Analysing Seasonal Health Data},
    author = {Adrian G Barnett and Annette J Dobson},
    publisher = {Springer},
    address = {Berlin, Heidelberg},
    year = {2010},
  }
  @Manual{,
    title = {season: Analysing Seasonal Data R Functions},
    author = {Adrian G Barnett and Peter J Baker and Annette J Dobson},
    year = {2-01},
    note = {R package version 0.3-1},
  }