@book { KundenbindungdurchCustomerRelationshipManagementCRM,
    title = "Kundenbindung durch Customer Relationship Management (CRM)",
    author = "Stephan {Mayer}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832482961",
    url = "https://m.diplom.de/document/223492"
}