Art in Wales: A Survey of 4000 Years to AD 1850, National Museum of Wales; Pernoud, R., Les Gaulois, Seuil, 1979; Pobé, M. The Art of Roman Gaul, London, 1962; Leeds, E. T., Celtic Ornament, Oxford, 1933; MacGregor, M. Early Celtic Art in North Britain, 2 vols., Leicester, 1976; and seventeen others of similar interest (23)