Priestley, M.J.N., Evison, R.J. and Carr, A.J. 1978. Seismic response of structures free to rock on their foundations. Bulletin of the New Zealand Society for Earthquake Engineering. 11, 3 (Sep. 1978), 141–150. DOI:https://doi.org/10.5459/bnzsee.11.3.141-150.