“The Effect of Adding Alumina Phases (alpha and Amorphous) to Improve the Mechanical Properties (Compressive Strength and Hardness) of Polyester Matrix Composites”. 2014. Journal of Engineering and Sustainable Development 18 (6): 202-11. https://jeasd.uomustansiriyah.edu.iq/index.php/jeasd/article/view/931.