To cite JOP in publications use:

Sonja Kuhnt, Nikolaus Rudak (2013). Simultaneous Optimization of Multiple Responses with the R Package JOP. Journal of Statistical Software, 54(9), 1-23. URL http://www.jstatsoft.org/v54/i09/.

Corresponding BibTeX entry:

  @Article{,
    title = {Simultaneous Optimization of Multiple Responses with the
      {R} Package {JOP}},
    author = {Sonja Kuhnt and Nikolaus Rudak},
    journal = {Journal of Statistical Software},
    year = {2013},
    volume = {54},
    number = {9},
    pages = {1--23},
    url = {http://www.jstatsoft.org/v54/i09/},
  }