@book { VoiceoverIPEineEinfhrungindieIPTelefonie, title = "Voice over IP - Eine Einführung in die IP Telefonie", author = "Robert {Nicola}", year = "2004", publisher = "GRIN Verlag", address = "München, Germany", doi = "10.3239/9783638279833", url = "https://www.hausarbeiten.de/document/25313" }