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Sitohang A-, Siregar M-. IMPROVING STUDENTS™ SPEAKING ACHIEVEMENT IN AGREEMENT AND DISAGREEMENT EXPRESSIONS BY USING PROBLEM SOLVING STRATEGY AT GRADE VIII SMP SWASTA HKBP SIDORAME MEDAN. TRANSFORM [Internet]. 15 Maret 2014 [dikutip 30 September 2026];3(1). Tersedia pada: https://jurnal.unimed.ac.id/2012/index.php/jelt/article/view/1819