@book { ECommerceinderHotellerie,
    title = "E-Commerce in der Hotellerie",
    author = "Manuela {Auer}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832430979",
    url = "https://m.diplom.de/document/218804"
}