Siragih HTI, Saragih MCI, Siabutar MNA. Analysis of Students’ Difficulties in Understanding the Concept of Summation in Grade II Students of UPTD State Elementary School 124407 Pematangsiantar. JPG [Internet]. 2026 Oct. 20 [cited 2026 Nov. 7];7(4):711-8. Available from: http://150.107.142.43/index.php/jpg/article/view/25450