@book { DasstarkeSelbst,
    title = "Das starke Selbst",
    author = "Falk {Rößler}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640992928",
    url = "https://www.hausarbeiten.de/document/177554"
}