@book { RelationshipMarketingundpersnlicherVerkauf,
    title = "Relationship Marketing und persönlicher Verkauf",
    author = "Agnieszka {Trojan}",
    year = "2005",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832489205",
    url = "https://m.diplom.de/document/224095"
}