@book { VirtuelleUnternehmen,
    title = "Virtuelle Unternehmen",
    author = "Markus {Bönig}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832429928",
    url = "https://m.diplom.de/document/218712"
}