@incollection{JM09,
  author        = {H. L. Jonker and S. Mauw},
  title         = {Discovering the core security requirements of DRM systems by means of objective trees},
  booktitle     = {Handbook of Research on Secure Multimedia Distribution},
  editor        = {Shiguo Lian and Yan Zhang},
  pages         = {71--85},
  publisher     = {IGI Global},
  isbn          = {978-1-60566-263-3},
  year          = {2009}
}