@book { CustomizationbeiPortalSites,
    title = "Customization bei Portal Sites",
    author = "Andreas {Hartmann}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832447182",
    url = "https://m.diplom.de/document/220321"
}