@book { MariaMontessorisReformkonzept,
    title = "Maria Montessoris Reformkonzept",
    author = "Lena {Heinrich}",
    year = "2009",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640431274",
    url = "https://www.hausarbeiten.de/document/135088"
}