Crespi Gabriella, Brass light sculpture from the Kaleidoscope series Engraved signature., Certificate of authenticity, Crespi, Italy, 1970 ca., W. 25 - D. 25 - H. 85 Cm, Literature, (curated by) C. Cunacchia, Gabriella Crespi, Il segno e lo spirito, pp. 14, 38, 94, Mondadori Electa, 2011.