@book { UbiquitousComputing,
    title = "Ubiquitous Computing",
    author = "Michael {Gillen}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832464028",
    url = "https://m.diplom.de/document/221829"
}