@book { PaneldatenmodellezurErklrungknftigerCashflows,
    title = "Paneldatenmodelle zur Erklärung künftiger Cashflows",
    author = "Frank {Spakowski}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836635530",
    url = "https://m.diplom.de/document/227181"
}