@book { Newsvendorprobleme,
    title = "Newsvendorprobleme",
    author = "Andy {Stephan}",
    year = "2010",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836645362",
    url = "https://m.diplom.de/document/227350"
}