@book { GreenIT,
    title = "Green IT",
    subtitle = "Marketinginstrument, Kostensenker und Umweltretter?",
    author = "Tobias {Hierl}",
    year = "2011",
    publisher = "BACHELOR + MASTER PUBLISHING",
    address = "Hamburg, Deutschland",
    url = "https://m.bachelor-master-publishing.de/document/296436"
}