TY  - RPRT
TI  - An improved model for the Earth's gravity field
AU  - Tapley, B. D.
AU  - Shum, C. K.
AU  - Yuan, D. N.
AU  - Ries, J. C.
AU  - Schutz, B. E.
PY  - 1989
UR  - https://ntrs.nasa.gov/citations/19900011199
ID  - 19900011199
ER  -