@book { Zeitmanagement,
    title = "Zeitmanagement ",
    author = "Heike {Vollborn}",
    year = "2009",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640332366",
    url = "https://www.hausarbeiten.de/document/126794"
}