@book { Betriebswirtschaftslehre,
    title = "Betriebswirtschaftslehre",
    author = "Marcus {Oehlrich} and Andreas {Dahmen}",
    year = "2019",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1221298"
}