@book { GeschftsmodelledesMBusiness,
    title = "Geschäftsmodelle des M-Business",
    author = "Heiko {Ahlke}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832456146",
    url = "https://m.diplom.de/document/221096"
}