@book { CustomerLifetimeValueBestimmungdesWertseinerKundenbeziehung,
    title = "Customer Lifetime Value: Bestimmung des Werts einer Kundenbeziehung",
    author = "Jan {Spethmann}",
    year = "2004",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638255431",
    url = "https://www.hausarbeiten.de/document/22115"
}