@book { GibtesdenidealenReisefhrer,
    title = "Gibt es den idealen Reiseführer?",
    author = "Aletta {Helsper}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832498788",
    url = "https://m.diplom.de/document/224995"
}