@book { TheKanbanSystemanditsRequirements,
    title = "The Kanban System and its Requirements",
    author = "Manuel {Ringwald}",
    year = "2013",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656453543",
    url = "https://www.hausarbeiten.de/document/229794"
}