@InProceedings {DS.esorics96,
    author = {S. {De Capitani di Vimercati} and P. Samarati},
    booktitle = {Proc. of the 4th European Symposium on Research in Computer Security, ESORICS'96},
    title = {An Authorization Model for Federated Systems},
    address = {Rome, Italy},
    month = {September},
    year = {1996}
}