@book { MarketingforschungundMarketingplanungimTourismus,
    title = "Marketingforschung und Marketingplanung im Tourismus",
    author = "Philipp {Arnold}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832496159",
    url = "https://m.diplom.de/document/224695"
}