To cite package ‘childfree’ in publications use:

  Neal, Z. P. and Neal, J. W. 2024. childfree: An R Package to Access
  and Harmonize Childfree Demographic Data. Comprehensive R Archive
  Network

A BibTeX entry for LaTeX users is

  @Article{,
    title = {childfree: An R Package to Access and Harmonize Childfree Demographic Data},
    author = {Zachary P. Neal and Jennifer Watling Neal},
    journal = {Comprehensive R Archive Network},
    year = {2024},
  }