@book { PreismanagementfrEBooks,
    title = "Preismanagement für E-Books",
    author = "Christopher {Forster}",
    year = "2012",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783842828056",
    url = "https://m.diplom.de/document/229120"
}