@book { InvestmentStrategies,
    title = "Investment Strategies",
    author = "Gerhard {Wörtche}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836639132",
    url = "https://m.diplom.de/document/227414"
}