@book { TheoretischesModellderOrgelimprovisation,
    title = "Theoretisches Modell der Orgelimprovisation",
    author = "Robert {Knappe}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832493363",
    url = "https://m.diplom.de/document/224456"
}