@book { ProblemedesnachhaltigenTourismusamTiticacaseeinPer,
    title = "Probleme des nachhaltigen Tourismus am Titicacasee in Perú",
    author = "Stefan {Siehl}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832495558",
    url = "https://m.diplom.de/document/224678"
}