@book { VonderKonvergenzzurDivergenz,
    title = "Von der Konvergenz zur Divergenz",
    author = "Marte {Helberg}",
    year = "1999",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832418014",
    url = "https://m.diplom.de/document/217657"
}