@book { DieProblematikderKundenbindungimReisebro,
    title = "Die Problematik der Kundenbindung im Reisebüro",
    subtitle = "Beziehungsmanagement für Reisemittler",
    author = "Janine {Gall}",
    year = "1998",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832412050",
    url = "https://m.diplom.de/document/217125"
}