@book { StrategienfrStadtwerkeimPortfoliomanagement,
    title = "Strategien für Stadtwerke im Portfoliomanagement",
    author = "Benjamin {Menge}",
    year = "2010",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783842807280",
    url = "https://m.diplom.de/document/228161"
}