@book { DerCO2Emissionshandel,
    title = "Der CO2-Emissionshandel",
    author = "Karl {Freudenthaler}",
    year = "2007",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836602280",
    url = "https://m.diplom.de/document/228809"
}