@book { CustomerRelationshipManagement,
    title = "Customer Relationship Management",
    author = "Asbjörn {Dudziak}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832447007",
    url = "https://m.diplom.de/document/220305"
}