JILANI, Saifuddin Ahmed; KHURSHEED, Kinza; MUKHTAR, Kamran. Comparative Study of F2–Layer Critical Frequency: Solar Cycle 22 : F2–Layer Critical Frequency . Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences, [S. l.], v. 55, n. 1, p. 35–46, 2021. Disponível em: http://ppaspk.org/index.php/PPAS-A/article/view/199. Acesso em: 4 dec. 2025.