To cite ldr in publications use:

Kofi P. Adragni, Andrew M. Raim (2014). ldr: An R Software Package for Likelihood-Based Sufficient Dimension Reduction. Journal of Statistical Software, 61(3), 1-21. URL http://www.jstatsoft.org/v61/i03/.

Corresponding BibTeX entry:

  @Article{,
    title = {{ldr}: An {R} Software Package for Likelihood-Based
      Sufficient Dimension Reduction},
    author = {Kofi P. Adragni and Andrew M. Raim},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {61},
    number = {3},
    pages = {1--21},
    url = {http://www.jstatsoft.org/v61/i03/},
  }