@InProceedings {bds-wint2003,
    author = {P. Bonatti and S. {De Capitani di Vimercati} and P. Samarati},
    booktitle = {Proc. of the Eleventh Cambridge International Workshop on Security Protocols},
    title = {Towards Flexible Credential Negotiation Protocols},
    address = {Cambridge, England},
    month = {April},
    year = {2003}
}