@book { BonusprogrammeinderPraxis,
    title = "Bonusprogramme in der Praxis",
    author = "Andrea {Heckmeier}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832467418",
    url = "https://m.diplom.de/document/222114"
}