Salal Al-Shouaily, N. R., and A. N. Abd Al-Amer. “The Effect Of Using Frank Lester’s Strategy In The Geometric Thinking Skills Of The Second Grade Intermediate School Female Students In Mathematics”. Opción, Vol. 35, Aug. 2019, pp. 735-56, https://produccioncientifica.luz.edu.ve/index.php/opcion/article/view/27426.