@book { DieLiberalisierungdesLuftverkehrs,
    title = "Die Liberalisierung des Luftverkehrs",
    author = "Malte  {Wilhelm} and Henning {Steffens}",
    year = "2014",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    url = "https://www.hausarbeiten.de/document/270844"
}