@book { DieSystemtheorieNiklasLuhmanns,
    title = "Die Systemtheorie Niklas Luhmanns",
    author = "Dominic {Lüthi}",
    year = "2006",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638565684",
    url = "https://www.hausarbeiten.de/document/63538"
}