@book { NetworkMarketingalsGeschftsidee,
    title = "Network Marketing als Geschäftsidee",
    author = "Jessika {Schulze}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836620307",
    url = "https://m.diplom.de/document/226226"
}