@book { NachhaltigerTourismusinSpanien,
    title = "Nachhaltiger Tourismus in Spanien",
    author = "Carmen {Spitzer}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832479190",
    url = "https://m.diplom.de/document/223165"
}