== Fem hypoteser ==
Shlionskiy oplister 15 mulige ''naturlige'' forklaringer i to grupper: Refleksioner i det ydre rum - og refleksioner inden for Jordens magnetosfære.<ref>[https://www.mn.uio.no/fysikk/english/people/aca/sverre/articles/shlionskiy15.html Sverre Holm summary, ''Shlionskiy's 15 possible explanations for Long Delayed Echoes'']</ref><ref>A. G. Shlionskiy, "Radio echos with multisecond delays," Telecommunications. and Radio Engineering, Vol 44, No. 12, pp. 48–51, December 1989.</ref> Vidmar og Crawford foreslår, at fem af dem er de mest sandsynlige.<ref name="vc85">R. J. Vidmar and F. W. Crawford, "Long-delayed radio echoes: Mechanisms and observations," Journal of Geophysical Research, vol. 90, no. A2, pp. 1523–1530, February 1985.</ref> Sverre Holm, professor i [[signalbehandling]] ved [[Universitetet i Oslo]] detaljerer disse fem;<ref name="Holm">[https://www.mn.uio.no/fysikk/english/people/aca/sverre/articles/lde.html Sverre Holm, ''The Five Most Likely Explanations for Long Delayed Echoes'']</ref> i opsummering,
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