@book { MarketingForschung,
    title = "Marketing-Forschung",
    author = "Stefan {Hoffmann} and Stefan {Wünschmann} and Anja {Franck} and Uta {Schwarz} and Katja {Soyez}",
    year = "2018",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1221294"
}