To cite ahaz in publications use:

  Anders Gorst-Rasmussen, Thomas H. Scheike (2012). Coordinate Descent
  Methods for the Penalized Semiparametric Additive Hazards Model.
  Journal of Statistical Software, 47(9), 1-17. URL
  https://www.jstatsoft.org/v47/i09/.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Coordinate Descent Methods for the Penalized Semiparametric Additive Hazards Model},
    author = {Anders Gorst-Rasmussen and Thomas H. Scheike},
    journal = {Journal of Statistical Software},
    year = {2012},
    volume = {47},
    number = {9},
    pages = {1--17},
    url = {https://www.jstatsoft.org/v47/i09/},
  }