@book { InteroperabilityofDRMSystems,
    title = "Interoperability of DRM Systems",
    subtitle = "Exchanging and Processing XML-based Rights Expressions",
    author = "Susanne {Guth}",
    year = "2006",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b13942",
    url = "https://www.peterlang.com/document/1068493"
}