@book { GruppenphasenKritischeEreignisseinGruppen,
    title = "Gruppenphasen - Kritische Ereignisse in Gruppen",
    author = "Bettina {Schmidt} and Jennifer {Schöttke}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640925407",
    url = "https://www.hausarbeiten.de/document/172571"
}