@book { WerbungfrdieZielgruppe50,
    title = "Werbung für die Zielgruppe 50+",
    author = "Christian {Schöler}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832449292",
    url = "https://m.diplom.de/document/220496"
}