To cite investr in publications use:

Brandon M. Greenwell and Christine M. Schubert Kabban (2014). investr: An R Package for Inverse Estimation. The R Journal, 6(1), 90-100. URL http://journal.r-project.org/archive/2014-1/greenwell-kabban.pdf.

Corresponding BibTeX entry:

  @Article{,
    title = {investr: An R Package for Inverse Estimation},
    author = {Brandon M. Greenwell and Christine M. Schubert Kabban},
    journal = {The R Journal},
    year = {2014},
    volume = {6},
    number = {1},
    pages = {90--100},
    url =
      {http://journal.r-project.org/archive/2014-1/greenwell-kabban.pdf},
  }