@book { VoiceoverIPversusklassischesFestnetz,
    title = "Voice over IP versus klassisches Festnetz",
    author = "Christopher {Krause}",
    year = "2013",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656397199",
    url = "https://www.hausarbeiten.de/document/211571"
}