@book { MainPlayeraufdemeuropischenGasmarkt,
    title = "Main Player auf dem europäischen Gasmarkt",
    author = "Patrick {Schwegmann}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832450205",
    url = "https://m.diplom.de/document/220170"
}