TY  - RPRT
TI  - Group Sunspot Numbers: Sunspot Cycle Characteristics
AU  - Hathaway, D. H.
AU  - Wilson, R. M.
AU  - Reichmann, E. J.
AU  - Six, N. Frank
PY  - 2002
UR  - https://ntrs.nasa.gov/citations/20020048587
ID  - 20020048587
ER  -