@book { SicherheitsbewertungderOpenSourceTelefonanlageSoftPBXAsterisk,
    title = "Sicherheitsbewertung der Open Source Telefonanlage (Soft-PBX) Asterisk",
    author = "Jens {Heidrich}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832495893",
    url = "https://m.diplom.de/document/224497"
}