@book { KidsMarketing,
    title = "Kids-Marketing",
    subtitle = "Die zunehmende Bedeutung der Marketingzielgruppe Kinder",
    author = "Ralf {Opalka}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832434502",
    url = "https://m.diplom.de/document/219118"
}