Stancheva, Anushka, Georgi Petrov, Plamen Tzvetkov, Angel Alexandrov, and Bilyana Benkova. “State of the Research on Solar Activity Impact on the Radio Waves Propagation”. Yearbook Telecommunications 2 (September 17, 2015): 29–38. Accessed November 21, 2024. https://ojs.nbu.bg/index.php/YT/article/view/182.