@book { DasDuzenundSiezen,
    title = "Das Duzen und Siezen",
    author = "Daniela {Hadwiger}",
    year = "2001",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640027996",
    url = "https://www.hausarbeiten.de/document/104464"
}