To cite the ropls package in publications use:

  Thevenot, E.A., Roux, A., Xu, Y., Ezan, E., Junot, C. 2015. Analysis
  of the human adult urinary metabolome variations with age, body mass
  index and gender by implementing a comprehensive workflow for
  univariate and OPLS statistical analyses. Journal of Proteome
  Research. 14: 3322-3335.

A BibTeX entry for LaTeX users is

  @Article{,
    author = {E. A. Thevenot and A. Roux and Y. Xu and E. Ezan and C. Junot},
    title = {Analysis of the human adult urinary metabolome variations with age, body mass index and gender by implementing a comprehensive workflow for univariate and OPLS statistical analyses},
    journal = {Journal of Proteome Research},
    year = {2015},
    volume = {14},
    pages = {3322-3335},
    url = {https://doi.org/10.1021/acs.jproteome.5b00354},
  }