@book { IstEuropaeinoptimalerWhrungsraum,
    title = "Ist Europa ein optimaler Währungsraum?",
    author = "Alexander {Charles}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836613217",
    url = "https://m.diplom.de/document/225794"
}