@Article {BCDDFPS.cose2010,
    author = {C. Blundo and S. Cimato and S. {De Capitani di Vimercati} and A. {De Santis} and S. Foresti and S. Paraboschi and P. Samarati},
    title = {Managing Key Hierarchies for Access Control Enforcement: Heuristic Approaches},
    journal = {Computers & Security},
    volume = {29},
    number = {5},
    pages = {533-547},
    month = {July},
    year = {2010}
}