@book { Sportmarketing,
    title = "Sportmarketing",
    author = "Monika {Oberndorfer}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832444815",
    url = "https://m.diplom.de/document/220083"
}