@book { EinfhrungvonGruppenarbeit,
    title = "Einführung von Gruppenarbeit",
    author = "Anja {vom Hofe}",
    year = "1999",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832417949",
    url = "https://m.diplom.de/document/217650"
}