TY  - RPRT
TI  - Approximations in the theory of solar-cycle modulation
AU  - Axford, W. I.
AU  - Fisk, L. A.
AU  - Gleeson, L. J.
PY  - 1970
UR  - https://ntrs.nasa.gov/citations/19710037413
ID  - 19710037413
ER  -