aa References

Copyright WDC C1 for STP at RAL.

• A hundred year series of geomagnetic data 1868 to 1967, indices aa, storm sudden commencements
  IAGA Bulletin 33 page 252, IUGG Publications Office, Paris 1973
  Author Mayaud, P.N.

• Derivation, Meaning, and Use of Geomagnetic Indices
  AGU (Washington D.C.), 1980.
  Author Mayaud, P.N.