@book { CustomerRelationshipManagementDerCustomerLifetimeValue,
    title = "Customer Relationship Management - Der Customer Lifetime Value",
    author = "Hendrik {Schneider}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656065852",
    url = "https://www.hausarbeiten.de/document/182214"
}