Effectiveness of Universal Concept of Mental Arithmetic System (UCMAS) In The Developing Of Visual Thinking Among Fourth Grade Students (Quasi- Experimental Study In Private Schools At Lattakia). TUJ-A [Internet]. 2017 Jan. 3 [cited 2026 Aug. 29];38(1). Available from: https://journal.latakia-univ.edu.sy/index.php/humlitr/article/view/2318