To cite package 'A3' in publications use:

Scott Fortmann-Roe (2013). Accurate, Adaptable and Accessible Error Metrics for Predictive Models. R package version 0.9.2.

Corresponding BibTeX entry:

  @Manual{,
    title = {Accurate, Adaptable and Accessible Model Error Metrics},
    author = {Scott Fortmann-Roe},
    year = {2013},
    note = {R package version 0.9.2},
  }