@book { Blauwestad,
    title = "Blauwestad",
    subtitle = "Recreation and Tourism in the Blauwestad - Monitoring and customer research",
    author = "Thomas {Töppel}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836636322",
    url = "https://m.diplom.de/document/227229"
}