To cite frbs in publications use:

Riza LS, Bergmeir C, Herrera F, Benítez JM (2015). “frbs: Fuzzy Rule-Based Systems for Classification and Regression in R.” Journal of Statistical Software, 65(6), 1–30. http://www.jstatsoft.org/v65/i06/.

Corresponding BibTeX entry:

  @Article{,
    title = {{frbs}: Fuzzy Rule-Based Systems for Classification and
      Regression in {R}},
    author = {Lala Septem Riza and Christoph Bergmeir and Francisco
      Herrera and Jos{\'e} Manuel Ben{\'i}tez},
    journal = {Journal of Statistical Software},
    year = {2015},
    volume = {65},
    number = {6},
    pages = {1--30},
    url = {http://www.jstatsoft.org/v65/i06/},
  }