Ionospheric Non-linear Effects Observed During Very-Long-Distance HF Propagation oleh Yuri Yampolski, Gennady Milikh, Andriy Zalizovski, Alexander Koloskov, Alexander Koloskov, Artem Reznichenko, Eliana Nossa, Eliana Nossa, Paul A. Bernhardt, Stan Briczinski, Savely M. Grach, Alexey Shindin, Evgeny Sergeev