@book { SpamRechtsfragenderEMailWerbung,
    title = "Spam - Rechtsfragen der E-Mail Werbung",
    author = "Andreas {Madel}",
    year = "2007",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836607704",
    url = "https://m.diplom.de/document/225475"
}