@book { MarketingPlanforthelaunchoftraveladvisernet,
    title = "Marketing Plan for the launch of traveladviser.net",
    author = "Thomas {Punzel}",
    year = "2009",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640266807",
    url = "https://www.hausarbeiten.de/document/122107"
}