1. The development of the auroral substorm
2. Albinson B (2018)Artiklar från Värmlands Brandhistoriska Klubb.http://www.brandhistoriska.org/artiklar/artiklar.pdf(Last accessed 29 January 2019)
3. Allen S(2019)Time scales https://www.ucolick.org/~sla/leapsecs/timescales.html(Last accessed 27 April2019)
4. The magnetic storm of May 13–14, 1921: Observations at Samoa Observatory;Angenheister G.;New Zealand Journal of Science and Technology,1921
5. The magnetic storm of May 13–16, 1921, at Apia Observatory, Samoa