@book { KundenbeziehungsmanagementinOpenSourceERPSystemen,
    title = "Kundenbeziehungsmanagement in Open-Source ERP-Systemen",
    author = "Lennart {Johansen}",
    year = "2010",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783842805125",
    url = "https://m.diplom.de/document/228070"
}