@Article {dps.spe,
    author = {S. {De Capitani di Vimercati} and S. Paraboschi and P. Samarati},
    title = {Access control: Principles and Solutions},
    journal = {Software - Practice and Experience},
    volume = {33},
    number = {5},
    month = {April},
    year = {2003}
}