@book { EinberblickberdasKonzeptdesCustomerRelationshipManagement,
    title = "Ein Überblick über das Konzept des Customer Relationship Management",
    author = "Frank {Holzmann}",
    year = "2005",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638355292",
    url = "https://www.hausarbeiten.de/document/35697"
}