@book { HabenFuballTestimonialseinebesserePerformance,
    title = "Haben Fußball-Testimonials eine bessere Performance?",
    author = "David {Kittelmann}",
    year = "2014",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    url = "https://m.diplom.de/document/271459"
}