@book { TrekkingTourismusinNepal,
    title = "Trekking-Tourismus in Nepal",
    author = "Kareen {Riedel}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836617055",
    url = "https://m.diplom.de/document/226020"
}