Ingham, J. M., M. J. N. Priestley, and F. Seible. “Seismic Response of Bridge Knee Joints Having Columns With Interlocking Spirals”. Bulletin of the New Zealand Society for Earthquake Engineering, vol. 30, no. 2, June 1997, pp. 114-32, doi:10.5459/bnzsee.30.2.114-132.