@book { TourismusaufdenPhilippinendieInselBoracay,
    title = "Tourismus auf den Philippinen - die Insel Boracay",
    author = "Michael {Sievritts}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832478681",
    url = "https://m.diplom.de/document/223121"
}