Garside, A., Jewellery: Ancient to Modern, Walters Art Gallery, Baltimore, New York, 1979; Schubnel, H.-J., Pierres de lumière et objets précieux, Paris, 1987; I Gioielli: G. Gregorietti, Milan, 1978; Zucker, B., Gemmes et joyaux, Geneva, 1988; Arem, J. E., Color Encylopedia of Gemstones, New York, 1977; Anderson Black, J., The Story of Jewellery, New York, 1974; Heiniger, E. A. and J., Le Grand Livre des Bijoux, Lausanne, 1974; and Ward, A., The Ring from Antiquity to the Twentieth Century, London, 1981 (8)