@book { DigitalRelationships,
    title = "Digital Relationships",
    author = "Tanja {Häussler}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832431105",
    url = "https://m.diplom.de/document/218817"
}