N. E.  Graham, Hughes, M. K., Ammann, C. M., Cobb, K. M., Hoerling, M. P., Kennett, D. J., Kennett, J. P., Rein, B., Stott, L., Wigand, P. E., and Xu, T. Y., ?Tropical Pacific - mid-latitude teleconnections in medieval times?, Climatic Change, vol. 83, no. 1-2, pp. 241-285, 2007.