@book { SprachentwicklunggeistigbehinderterKinder,
    title = "Sprachentwicklung geistig behinderter Kinder",
    author = "Albin {Muff}",
    year = "2009",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640280568",
    url = "https://www.hausarbeiten.de/document/123309"
}