@book { VirtualRealitiesimInternet,
    title = "Virtual Realities im Internet",
    author = "Astrid {Otto}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832427849",
    url = "https://m.diplom.de/document/218518"
}