@book { JeanPiagetsTheoriederkognitivenEntwicklung,
    title = "Jean Piagets Theorie der kognitiven Entwicklung",
    author = "Katja {Kuhn}",
    year = "2005",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638428002",
    url = "https://www.hausarbeiten.de/document/45383"
}