TY  - RPRT
TI  - Some effects of quiet geomagnetic field changes upon values used for main field modeling
AU  - W.H. Campbell
PY  - 1987
DO  - 10.1016/0031-9201(87)90144-0
UR  - https://pubs.usgs.gov/publication/70014219
ID  - 70014219
ER  -