@article{Power_et_al_2008,
  title = "On formalising and normalising role-based access control systems",
  author = "D. J. Power, M. A. Slaymaker, and A. C. Simpson",
  year = "2009",
  journal = "The Computer Journal",
  number = "3",
  pages = "305-325",
  volume = "52",
  doi = "doi:10.1093/comjnl/bxn016",
}