To cite package 'Rothermel' in publications use:

Giorgio Vacchiano, Davide Ascoli (2014). An implementation of the Rothermel fire spread model in the R programming language. Fire Technology. doi:10.1007/s10694-014-0405-6

Corresponding BibTeX entry:

  @Article{,
    title = {An implementation of the Rothermel fire spread model in
      the R programming language},
    author = {Giorgio Vacchiano and Davide Ascoli},
    year = {2014},
    journal = {Fire Technology},
    note = {DOI 10.1007/s10694-014-0405-6},
  }