@book { VergleichvonTelekommunikationsundStromtarifen,
    title = "Vergleich von Telekommunikations- und Stromtarifen",
    author = "Thorsten {Heisig}",
    year = "1999",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832415853",
    url = "https://m.diplom.de/document/217425"
}