@book { Schwangerschaftsgymnastik,
    title = "Schwangerschaftsgymnastik",
    author = "Heike {Höfler}",
    year = "2011",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/403262"
}