1. Outage of the L-4 system and the geomagnetic disturbances of August 4, 1972;Anderson;Bell System Technology Journal,1974
2. The magnetic storm of May 13-14, 1921: observations at Samoa Observatory;Angenheister;New Zealand Journal of Science and Technology,1921
3. Elovaara, J., Linblad, P., Viljanen, A., Makinen, T., Pirjola, R., Larsson, S., Kielen, B. Geomagnetically Induced Currents in the Nordic Power System and their Effects on Equipment, Control, Protection and Operation, CIGRE Paper 36-301, 1992 Session, 1992.
4. Erinmez, I.A., Majithia, S., Rogers, C., Yasuhiro, T., Ogawa, S., Swahn, H., Kappenman, J.G.. Application of Modeling Techniques to Assess Geomagnetically Induced Current Risks on the NGC Transmission System, CIGRE Paper 39-304, Session 2002, 2002.
5. Results of Observations made at the United States Coast and Geodetic Survey Magnetic Observatory at Cheltenham, MD, in 1921 and 1922;Hazard,1924