@book { Backpacking20,
    title = "Backpacking 2.0",
    author = "Christof {Hofstätter}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836620956",
    url = "https://m.diplom.de/document/226270"
}