@book { DasCallCenteralsinnovativesMarketinginstrument,
    title = "Das Call Center als innovatives Marketinginstrument",
    author = "Tobias {Weil}",
    year = "1998",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832408923",
    url = "https://m.diplom.de/document/216793"
}