ROBINSON, W. H.; GANNON, C. A RoBall with an elastic restoring force. Bulletin of the New Zealand Society for Earthquake Engineering, [S. l.], v. 39, n. 1, p. 85–88, 2006. DOI: 10.5459/bnzsee.39.1.85-88. Disponível em: https://bulletin.nzsee.org.nz/article/view/380. Acesso em: 13 jun. 2026.