@book { AgileRetrospektiven,
    title = "Agile Retrospektiven",
    author = "Esther {Derby} and Diana {Larsen} and Luitgard {Köster}",
    year = "2018",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1219106"
}