@book { Sporteventsponsoring,
    title = "Sporteventsponsoring",
    author = "Petra {Mathi}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832443313",
    url = "https://m.diplom.de/document/219931"
}