@book { TeleshoppinginDeutschland,
    title = "Teleshopping in Deutschland",
    author = "Stefan {Harder}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832435523",
    url = "https://m.diplom.de/document/219213"
}