[1]Hồng, P.T.T. et al. 2013. Ionospheric conductivity from the ionograms recorded at Phu Thuy, Hanoi. <i>Vietnam Journal of Earth Sciences</i>. 34, 4 (Mar. 2013), 524–534. DOI:https://doi.org/10.15625/0866-7187/34/4/2812.