@book { SeniorenmarketingimTourismus,
    title = "Seniorenmarketing im Tourismus",
    author = "Janine {Trobisch}",
    year = "2007",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836601115",
    url = "https://m.diplom.de/document/228763"
}