@book { AufbaueinerZementfabrikinLibyen,
    title = "Aufbau einer Zementfabrik in Libyen",
    author = "Matthias {Dupke}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836639552",
    url = "https://m.diplom.de/document/227432"
}