@book { RelationshipMarketingimInternet,
    title = "Relationship Marketing im Internet",
    author = "Steffen {Busse}",
    year = "2001",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638101646",
    url = "https://www.hausarbeiten.de/document/218"
}