@book { VoiceoverIPinderberuflichenSchule,
    title = "Voice over IP in der beruflichen Schule",
    author = "Jürgen {Hütter}",
    year = "2013",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656533368",
    url = "https://www.hausarbeiten.de/document/263304"
}