@book { MindfulnessDasPrinzipAchtsamkeit,
    title = "Mindfulness: Das Prinzip Achtsamkeit",
    author = "Ellen J. {Langer} and Ilse {Strasmann}",
    year = "2015",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1220941"
}