@book { CustomerLifetimeValueManagement,
    title = "Customer Lifetime Value Management",
    author = "Matthias {Arnold}",
    year = "2005",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638361262",
    url = "https://www.hausarbeiten.de/document/36526"
}