@book { Unternehmensfhrung,
    title = "Unternehmensführung",
    author = "Wolfgang {Burr} and Michael {Stephan} and Clemens {Werkmeister}",
    year = "2012",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1220785"
}