@inproceedings{JSVaidyaSacmat07coll,
  author = "Janice Warner and Vijay Atluri and Ravi Mukkamala and Jaideep
Vaidya",
  title = "Collaboration Based Access Control Using Semantics", 
  booktitle = "The Twelth ACM Symposium on Access Control Models and 
Technologies",
  address = "Sophia Antipolis, France",
  month = jun # "20-22",
  pages = "235--244",
  year = 2007
}