To cite fda.usc in publications use:

Manuel Febrero-Bande, Manuel Oviedo de la Fuente (2012). Statistical Computing in Functional Data Analysis: The R Package fda.usc. Journal of Statistical Software, 51(4), 1-28. URL http://www.jstatsoft.org/v51/i04/.

Corresponding BibTeX entry:

  @Article{,
    title = {Statistical Computing in Functional Data Analysis: The {R}
      Package {fda.usc}},
    author = {Manuel Febrero-Bande and Manuel {Oviedo de la Fuente}},
    journal = {Journal of Statistical Software},
    year = {2012},
    volume = {51},
    number = {4},
    pages = {1--28},
    url = {http://www.jstatsoft.org/v51/i04/},
  }