To cite MatchIt in publications use:

Ho DE, Imai K, King G, Stuart EA (2011). “MatchIt: Nonparametric Preprocessing for Parametric Causal Inference.” Journal of Statistical Software, 42(8), 1–28. doi:10.18637/jss.v042.i08.

Corresponding BibTeX entry:

  @Article{,
    title = {{MatchIt}: Nonparametric Preprocessing for Parametric
      Causal Inference},
    author = {Daniel E. Ho and Kosuke Imai and Gary King and Elizabeth
      A. Stuart},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {42},
    number = {8},
    pages = {1--28},
    doi = {10.18637/jss.v042.i08},
  }