To cite package ‘PTwins’ in publications use:

Aznar R, Esteban L, Sanz G, Saviron R (2019). PTwins: Percentile Estimation of Fetal Weight for Twins by Chorionicity. R package version 0.1.1, https://CRAN.R-project.org/package=PTwins.

Corresponding BibTeX entry:

  @Manual{,
    title = {PTwins: Percentile Estimation of Fetal Weight for Twins by
      Chorionicity},
    author = {Rocio Aznar and Luis Mariano Esteban and Gerardo Sanz and
      Ricardo Saviron},
    year = {2019},
    note = {R package version 0.1.1},
    url = {https://CRAN.R-project.org/package=PTwins},
  }