@book { KennzahlensystemefrdasITControlling,
    title = "Kennzahlensysteme für das IT-Controlling",
    author = "Enrico {Ebert}",
    year = "2007",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638805414",
    url = "https://www.hausarbeiten.de/document/76664"
}