J. S.  Bobowski, Baglo, J. C., Day, J., Dosanjh, P., Ofer, R., Ramshaw, B. J., Liang, R., Bonn, D. A., Hardy, W. N., Luo, H., Wang, Z. - S., Fang, L., and Wen, H. - H., ?Precision microwave electrodynamic measurements of K- and Co-doped?, Physical Review B, vol. 82, no. 9, 2010.