Z. Kang

Tapley, B., Ries, J. C., Bettadpur, S., Chambers, D., Cheng, M., Condi, F., … Wang, F. (2005). GGM02 An improved Earth gravity field model from GRACE. Journal of Geodesy, 79, 467–478. http://doi.org/10.1007/s00190-005-0480-z (Original work published November 2005)

Kang, Z., Tapley, B., Chen, J., Ries, J. C., & Bettadpur, S. (2009). Geocenter variations derived from GPS tracking of the GRACE satellites. Journal of Geodesy, 83, 895–901. http://doi.org/10.1007/s00190-009-0307-4 (Original work published October 2009)