Atena, Rivera. “Flexibility and Adaptability of Secondary School Managers to 21st Century Skills”. International Journal of Sciences: Basic and Applied Research (IJSBAR) 40, no. 2 (August 21, 2018): 169–185. Accessed October 6, 2025. https://gssrr.org/JournalOfBasicAndApplied/article/view/9123.