@book { ControllinginmittlerenUnternehmensberatungen,
    title = "Controlling in mittleren Unternehmensberatungen",
    author = "Stefan {Seibert}",
    year = "2011",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783842814639",
    url = "https://m.diplom.de/document/228501"
}