To cite A3 in publications use:

Fortmann-Roe S (2015). “Consistent and Clear Reporting of Results from Diverse Modeling Techniques: The A3 Method.” Journal of Statistical Software, 66(7), 1–23. http://www.jstatsoft.org/v66/i07/.

Corresponding BibTeX entry:

  @Article{,
    title = {Consistent and Clear Reporting of Results from Diverse
      Modeling Techniques: The A3 Method},
    author = {Scott Fortmann-Roe},
    journal = {Journal of Statistical Software},
    year = {2015},
    volume = {66},
    number = {7},
    pages = {1--23},
    url = {http://www.jstatsoft.org/v66/i07/},
  }