حسينأ.م.د. هدى. 2019. “The Effectiveness of Using Learning Centers Strategy Upon Conceptual Comprehension and Retention in History Subject for the Fifth Class Preporatory Students”. ALUSTATH JOURNAL FOR HUMAN AND SOCIAL SCIENCES 1 (7), 103-28. http://alustath.uobaghdad.edu.iq/index.php/UJIRCO/article/view/959.