ON THE GINZBURG-FEINBERG PROBLEM OF FREQUENCY ELECTROMAGNETIC SOUNDING FOR UNAMBIGUOUS DETERMINATION OF THE ELECTRON DENSITY IN THE IONOSPHERE. ENVIRONMENT. TECHNOLOGY. RESOURCES. Proceedings of the International Scientific and Practical Conference, [S. l.], v. 3, p. 89–96, 2017. DOI: 10.17770/etr2017vol3.2561. Disponível em: https://archive-journals.rtu.lv/etr/article/view/4129.. Acesso em: 11 mar. 2026.