To cite optmatch in publications use:

Hansen BB, Klopfer SO (2006). “Optimal full matching and related designs via network flows.” Journal of Computational and Graphical Statistics, 15(3), 609–627.

Corresponding BibTeX entry:

  @Article{,
    author = {Ben B. Hansen and Stephanie Olsen Klopfer},
    title = {Optimal full matching and related designs via network
      flows},
    keywords = {matched sampling, minimum cost flow, nonrandom
      treatment assignment, observational study, quasiexperiment,
      subclassification},
    journal = {Journal of Computational and Graphical Statistics},
    volume = {15},
    number = {3},
    pages = {609--627},
    year = {2006},
  }