@book { MarktkommunikationundInternet,
    title = "Marktkommunikation und Internet",
    author = "Gerald {Trajer}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832449056",
    url = "https://m.diplom.de/document/220474"
}