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2. Wenn der Geist die Materie küsst, ed. K. Griesar, Deutsch Harri GmbH, Frankfurt am Main, Germany, 2004
3. P. Ball , Bright Earth: Art and the Invention of Colour, Farrar, Straus and Giroux, New York, USA, 2001
4. D. Lewis-Williams , The Mind in the Cave: Consciousness and the Origins of Art, Thames and Hudson, London, UK, 2002