Ma, Quincy T., and John W. Butterworth. “Simplified Expressions for Modelling Rigid Rocking Structures on Two-Spring Foundations”. Bulletin of the New Zealand Society for Earthquake Engineering 45, no. 1 (March 31, 2012): 31–39. Accessed May 14, 2026. https://bulletin.nzsee.org.nz/article/view/212.