@book { TUIanditsMarketingPlan,
    title = "TUI and its Marketing Plan",
    author = "Kerstin {Schneider}",
    year = "2012",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656247678",
    url = "https://www.hausarbeiten.de/document/197946"
}