@book { VariantendesCAPM,
    title = "Varianten des CAPM",
    author = "Roland {Schröter}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832467807",
    url = "https://m.diplom.de/document/222135"
}