To cite FME in publications use:

  Soetaert, Karline and Petzoldt, Thomas, 2010. Inverse Modelling,
  Sensitivity and Monte Carlo Analysis in R Using Package FME. Journal
  of Statistical Software, 33(3), 1-28. doi:10.18637/jss.v033.i03

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Inverse Modelling, Sensitivity and Monte Carlo Analysis in {R} Using Package {FME}},
    author = {{Karline Soetaert} and {Thomas Petzoldt}},
    journal = {Journal of Statistical Software},
    year = {2010},
    volume = {33},
    number = {3},
    pages = {1--28},
    doi = {10.18637/jss.v033.i03},
  }