@book { SportzuschauerimFuball,
    title = "Sportzuschauer im Fußball",
    subtitle = "Empirische Analyse am Beispiel des SC Freiburg",
    author = "Elena {Neidhardt}",
    year = "1999",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832414719",
    url = "https://m.diplom.de/document/217321"
}