@book { InternetundJugendschutz,
    title = "Internet und Jugendschutz",
    author = "Ferdinand {Offner}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832466824",
    url = "https://m.diplom.de/document/222060"
}