@book { MarketinginderWeiterbildung,
    title = "Marketing in der Weiterbildung",
    author = "Johannes {Schreiber}",
    year = "2011",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783842812222",
    url = "https://m.diplom.de/document/228420"
}