Eissa, Abdelrahman Elsaid, and Mohamed AbdelShakour 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/JournalOfBasicAndApplied/article/view/10746.