@book { VirtuelleUniversitten,
    title = "Virtuelle Universitäten",
    subtitle = "State of the art - Analyse und Entwicklungstendenzen",
    author = "Christian {Schawel}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832448646",
    url = "https://m.diplom.de/document/220433"
}