@book { MessungvonNetzeffekteninTheorieundPraxis,
    title = "Messung von Netzeffekten in Theorie und Praxis",
    author = "Thomas {Röhrig}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832448950",
    url = "https://m.diplom.de/document/220464"
}