To cite ipw in publications use:

van der Wal WM, Geskus RB (2011). “ipw: An R Package for Inverse Probability Weighting.” Journal of Statistical Software, 43(13), 1–23. doi:10.18637/jss.v043.i13.

Corresponding BibTeX entry:

  @Article{,
    title = {{ipw}: An {R} Package for Inverse Probability Weighting},
    author = {Willem M. {van der Wal} and Ronald B. Geskus},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {43},
    number = {13},
    pages = {1--23},
    doi = {10.18637/jss.v043.i13},
  }