To cite 'HAC' in publications use:

Ostap Okhirn and Alexander Ristig (2012). Hierarchical Archimedean Copulae: The HAC Package. Discussion Paper 2012-36, CRC 649, Economic Risk. URL http://sfb649.wiwi.hu-berlin.de/papers/pdf/SFB649DP2012-036.pdf.

Corresponding BibTeX entry:

  @TechReport{,
    title = {Hierarchical {A}rchimedean Copulae: The {HAC} Package},
    author = {Ostap Okhrin and Alexander Ristig},
    institution = {CRC 649, Economic Risk},
    year = {2012},
    type = {Discussion paper},
    number = {2012, 036},
    url =
      {http://sfb649.wiwi.hu-berlin.de/papers/pdf/SFB649DP2012-036.pdf},
  }