Eissa, A. E. ., and M. A. . Hasan. “Modal Analysis of Prestressed Concrete Structural System for Wind Turbine Tower”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 49, no. 2, Feb. 2020, pp. 108-1, https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/10746.