@book { RckertskleineRckenschule,
    title = "Rückerts kleine Rückenschule",
    author = "Uwe {Rückert}",
    year = "2012",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/404178"
}