@book { UltraschallKurs,
    title = "Ultraschall-Kurs",
    author = "Christoph F. {Dietrich}",
    year = "2021",
    publisher = "Deutscher Ärzteverlag",
    address = "Köln, Germany",
    doi = "10.47420/9783769137156",
    url = "https://deutscheraerzteverlag.openpublishing.com/document/961281"
}