Umar B, Jatmiko B, Raharjo R. DEVELOPMENT OF NATURAL SCIENCE LEARNING INSTRUMENTS WITH CONTEXTUAL APPROACH USING PROBLEM SOLVING MODEL TO IMPROVE CRITICAL THINKING SKILL OF JUNIOR HIGH SCHOOL STUDENTS. J. penelitian. pendidik. sains [Internet]. 2018 Jun. 26 [cited 2025 Jun. 14];7(2):1501-6. Available from: https://journal.unesa.ac.id/index.php/jpps/article/view/2931