@book { AltersvorsorgedurchPensionsfonds,
    title = "Altersvorsorge durch Pensionsfonds",
    author = "Tanja {Michelberger}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832430672",
    url = "https://m.diplom.de/document/218779"
}