@book { DasBarcelonaPrinzip,
    title = "Das Barcelona-Prinzip",
    subtitle = "Die Dreisprachigkeit aller Europäer als sprachenpolitisches Ziel der EU",
    author = "Jan {Kruse}",
    year = "2012",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1108970"
}