To cite 'Matching' in publications use:

Sekhon JS (2011). “Multivariate and Propensity Score Matching Software with Automated Balance Optimization: The Matching Package for R.” Journal of Statistical Software, 42(7), 1–52. doi: 10.18637/jss.v042.i07.

To refer to the theory on which this package is based:

Diamond A, Sekhon JS (2013). “Genetic Matching for Estimating Causal Effects: A General Multivariate Matching Method for Achieving Balance in Observational Studies.” Review of Economics and Statistics, 95(3), 932–945. http://sekhon.berkeley.edu/papers/GenMatch.pdf.

Further developing the theory and practice:

Sekhon JS, Grieve RD (2012). “A Matching Method For Improving Covariate Balance in Cost-Effectiveness Analyses.” Health Economics, 21(6), 695–714.

BibTeX entries for LaTeX users: use ‘toBibtex(citation("Matching"))’

Corresponding BibTeX entries:

  @Article{,
    title = {Multivariate and Propensity Score Matching Software with
      Automated Balance Optimization: The {Matching} Package for {R}},
    author = {Jasjeet S. Sekhon},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {42},
    number = {7},
    pages = {1--52},
    doi = {10.18637/jss.v042.i07},
  }

  @Article{,
    title = {Genetic Matching for Estimating Causal Effects: A General
      Multivariate Matching Method for Achieving Balance in
      Observational Studies},
    author = {Alexis Diamond and Jasjeet S. Sekhon},
    journal = {Review of Economics and Statistics},
    volume = {95},
    number = {3},
    pages = {932--945},
    year = {2013},
    url = {http://sekhon.berkeley.edu/papers/GenMatch.pdf},
  }

  @Article{,
    title = {A Matching Method For Improving Covariate Balance in
      Cost-Effectiveness Analyses},
    author = {Jasjeet Singh Sekhon and Richard D. Grieve},
    journal = {Health Economics},
    volume = {21},
    number = {6},
    pages = {695--714},
    year = {2012},
  }